This just started happening after I made update on Twitch to the latest version. I had the version immediately prior, and this issue did not happen. So it seems reasonable to believe this has occurred as a result of a change made in this latest version. Note, the bag does open, but none of the slots show content. It's just showing the top header portion of the guild bank.

https://i.imgur.com/pn6fN3C.jpg

Date: 2018-09-07 22:30:29
ID: 12
Error occured in: Global
Count: 1
Message: ...nterface\AddOns\Bagnon_GuildBank\components\item.lua line 26:
attempt to concatenate local 'id' (a nil value)
Debug:
(tail call): ?
[C]: ?
...nterface\AddOns\Bagnon_GuildBank\components\item.lua:26: Construct()
...AddOns\Bagnon\external\Wildpants\components\item.lua:37: Create()
...nterface\AddOns\Bagnon_GuildBank\components\item.lua:16: Create()
...AddOns\Bagnon\external\Wildpants\components\item.lua:22: New()
...s\Bagnon\external\Wildpants\components\itemFrame.lua:119:
...s\Bagnon\external\Wildpants\components\itemFrame.lua:108
Locals:
(*temporary) = 0.016000000759959
(*temporary) = defined =[C]:-1

AddOns:
Swatter, v7.7.6095 (SwimmingSeadragon)
AccountantClassic, vv2.11.03
AdvancedInterfaceOptions, v1.2.4
AtlasLoot, vv8.07.13
AtlasLootBurningCrusade, vv8.07.13
AtlasLootCataclysm, vv8.07.13
AtlasLootClassic, vv8.07.13
AtlasLootLegion, vv8.07.13
AtlasLootMistsofPandaria, vv8.07.13
AtlasLootWarlordsofDraenor, vv8.07.13
AtlasLootWrathoftheLichKing, vv8.07.13
AucAdvanced, v7.7.6112 (SwimmingSeadragon)
AucFilterBasic, v7.7.6081 (SwimmingSeadragon)
AucStatHistogram, v7.7.6083 (SwimmingSeadragon)
AucStatiLevel, v7.7.6087 (SwimmingSeadragon)
AucStatPurchased, v7.7.6084 (SwimmingSeadragon)
AucStatSimple, v7.7.6085 (SwimmingSeadragon)
AucStatStdDev, v7.7.6086 (SwimmingSeadragon)
AucUtilFixAH, v7.7.6088 (SwimmingSeadragon)
Auctionator, v5.0.5
AuctionatorMiniFeatures, v8.0v1-release
BagBrother, v
Bagnon, v8.0.4
BagnonGuildBank, v8.0.4
BattlePetCounter, v
BelowAverageItems, v1.27
BigWigs, vv108.1
BrokerPortals, v1.10.0
Clique, vv80000-1.0.0
DBMCore, v8.0.6
DBMDefaultSkin, v
DBMStatusBarTimers, v
DejaCharacterStats, v800r103
Details, v
DetailsDmgRank, v
DetailsDpsTuning, v
DetailsEncounterDetails, v
DetailsRaidCheck, v
DetailsStreamer, v
DetailsTimeAttack, v
DetailsTinyThreat, v
DetailsVanguard, v
Dominos, v8.0.7
DominosCast, v
DominosEncounter, v
DominosProgress, v
DominosRoll, v
EasyObliterate, v31
FollowerLocationInfo, v1.5.2-release
FollowerLocationInfoJournal, v1.5.2-release
HandyNotes, vv1.5.3
HandyNotesAchievements, v0.4.20
HandyNotesAncientShrines, v2.0
HandyNotesArgus, vv0.10
HandyNotesAzerothsTopTunes, vv1.2.2
HandyNotesBrokenShore, vv1.29
HandyNotesCamelFigurines, v1.3
HandyNotesCityGuide, v1.7.1
HandyNotesDirections, v1
HandyNotesDraenorTreasures, v1.21
HandyNotesDungeonLocations, v1.35
HandyNotesEagleFlightNetwork, v1.0
HandyNotesEliteBattlePets, v1
HandyNotesEverShiftingMirror, v1.0.3
HandyNotesFieldPhotographer, v8.0.0.0
HandyNotesGuild, v1.10
HandyNotesHallowsEnd, vv1.3
HandyNotesHigherDimensionalLearning, v1
HandyNotesHigherLearning, v8.0.0.0
HandyNotesKosumoth, v1
HandyNotesLegionClassOrderHalls, vv1.29
HandyNotesLegionInstanceWorldQuests, vv1.15
HandyNotesLegionMagePortals, v1.3
HandyNotesLegionRaresTreasures, v1.1
HandyNotesLegionTownPortals, v0.0.1
HandyNotesLegionTreasures, v1
HandyNotesLongForgottenHippogryph, v1
HandyNotesLorewalkers, v1
HandyNotesLostAndFound, v1
HandyNotesLunarFestival, vv1.5
HandyNotesMailboxes, v1
HandyNotesPandariaTreasures, v1.06
HandyNotesPetDailies, v
HandyNotesSpecialNPCsEtc, v1.1.1-Beta
HandyNotesSummerFestival, vv1.5
HandyNotesSuramarLeylines, v1
HandyNotesSuramarLocations, v0.0.1
HandyNotesSuramarShalAranTelemancy, vv1.19
HandyNotesSuramarTelemancy, v1
HandyNotesTimelessIsleRareElites, v2.32
HandyNotesTimelessIsleChests, v1.20
HandyNotesTimelessTreasures, v1.0.7
HandyNotesTrainers, v1.7.0
HandyNotesTravelGuide, vv1.9.2
HandyNotesTreasureHunter, v1
HandyNotesVendors, v1.7.0
HandyNotesWellRead, v8.0.0.0
HandyNotesWitheredArmyTraining, v1
HandyNotesWitheredChests, v1.2
HealBot, v8.0.1.0
HealBotTips, v8.0.1.0
IceHUD, v1.11.5
ImprovedOptionsFrames, v1.5.6
InFlightLoad, v8.0.003
Informant, v7.7.6092 (SwimmingSeadragon)
InstancePortals, v19
MarketWatcher, v2.21
MasterPlanA, vA
MikScrollingBattleText, v5.7.149
OPie, vVanilla 7
Overachiever, v1.0.3
OverachieverCache, v1.0.3
OverachieverTabs, v1.0.3
Pawn, v2.2.28
PersonalLootHelper, v2.17
PetBattleFFVictory, vv1.2.6
PetBattleJunkie, v1.5
PetBattleMaster, v8.0.0
PetTracker, v8.0.6
PetTrackerBreeds, v8.0.6
PetTrackerJournal, v8.0.6
PetTrackerSwitcher, v8.0.6
PetTrackerUpgrades, v8.0.6
PGFinder, v5.8
Recount, vv8.0.1b
SavedInstances, v8.0.5
SlideBar, v7.7.6093 (SwimmingSeadragon)
Stubby, v7.7.6094 (SwimmingSeadragon)
TargetPercent, vv8.0.0
TellMeWhen, v8.5.3
Titan, v5.14.7.80000
TitanBag, v5.14.7.80000
TitanClock, v5.14.7.80000
TitanGold, v5.14.7.80000
TitanLocation, v5.14.7.80000
TitanLootType, v5.14.7.80000
TitanPerformance, v5.14.7.80000
TitanRepair, v5.14.7.80000
TitanVolume, v5.14.7.80000
TitanXP, v5.14.7.80000
TomTom, vv80001-1.0.2
TradeSkillMaster, vv4.3.1
TradeSkillMasterAppHelper, vv4.0
WorldQuestTracker, v
WoWPro, v8.0.1H
WoWProAchievements, v8.0.1H
WoWProDailies, v8.0.1H
WoWProLeveling, v8.0.1H
WowProProfession, v8.0.1H
WoWProWorldEvents, v8.0.1H
BlizRuntimeLib_enUS v8.0.1.80000
(ck=11d2)

Hey I found part of the issue, in the file item.lua located at "World of Warcraft\Interface\AddOns\Bagnon_GuildBank\components". On line 26 is the code: return CreateFrame('Button', MODULE .. 'ItemSlot' .. id, nil, 'ContainerFrameItemButtonTemplate'). If you remove the id in front of "'ItemSlot' .." the guild bank tab will open, but Bagnon will still throw an error, and it appears that the guild bank tab can be viewed, but not interacted with.

m not seeing what is in my guild bank at all.

Message: ...nterface\AddOns\Bagnon_GuildBank\components\item.lua:26: attempt to concatenate local 'id' (a nil value)
Time: Sat Sep 8 17:16:16 2018
Count: 1
Stack: ...nterface\AddOns\Bagnon_GuildBank\components\item.lua:26: attempt to concatenate local 'id' (a nil value)
...nterface\AddOns\Bagnon_GuildBank\components\item.lua:26: in function Construct' ...AddOns\Bagnon\external\Wildpants\components\item.lua:37: in function Create'
...nterface\AddOns\Bagnon_GuildBank\components\item.lua:16: in function Create' ...AddOns\Bagnon\external\Wildpants\components\item.lua:22: in function New'
...s\Bagnon\external\Wildpants\components\itemFrame.lua:119: in function <...s\Bagnon\external\Wildpants\components\itemFrame.lua:108>

Locals: self = {
0 =
OnEnter = defined @interface\AddOns\Bagnon_GuildBank\components\item.lua:74
__super = {
}
IsNew = defined @interface\AddOns\Bagnon_GuildBank\components\item.lua:119
UpdateCooldown = defined @interface\AddOns\Bagnon_GuildBank\components\item.lua:105
GetBlizzard = defined @interface\AddOns\Bagnon_GuildBank\components\item.lua:29
OnDragStart = defined @interface\AddOns\Bagnon_GuildBank\components\item.lua:62
OnReceiveDrag = defined @interface\AddOns\Bagnon_GuildBank\components\item.lua:68
__index = {
}
unused =

Did nothing more than DOWNGRADE to 8.0.3 from 8.0.4, and it works again. So this, I think, demonstrates that something in 8.0.4 is either broken, or conflicting:

https://i.imgur.com/DFSg8Xz.jpg