Newest versions: 1.2.0 and 1.2.1 breaks all the Arcane Workbench recipes that require Vis Crystals in Thaumcraft BETA26.
1.1.0 version of Fancy Lamps doesn't have this issue.

Was there ever anything figured out here? Is the mod still maintained?

@Orinai To be honest, I never figured it out as I just continued using 1.1.0 version of the mod.

I haven't touched the mod in a while, but I've just tried again with 1.2.1 FancyLamps and BETA26 Thaumcraft finding no errors. I'd need some logs to be able to identify an issue though.

This definitely doesn't happen for me with TC and FancyLamps alone, do you have a mod list?

Edit: Thought that .zip for importing mod pack all together in Twitch Desktop App would be more of use than just plain mod list since it has all correct mod versions and configs I'm using.
https://www.dropbox.com/s/sayeotegimqdepa/TBV%20Lite-20.4.23.zip?dl=0

Sure thing, here you go:

• Just Enough Resources (JER) (by way2muchnoise)
• Better Builder's Wands (by Portablejim)
• LunatriusCore (by Lunatrius)
• Stackie (by Lunatrius)
• Just Enough HarvestCraft (JEHC) (by mrAppleXZ)
• Cosmetic Armor Reworked (by LainMI)
• Stargate Network (by Almura_Dockter)
• Storage Drawers Unlimited (by raptor4694)
• Natura (by mDiyo)
• Morpheus (by Quetzi)
• More Overlays (by FeldiM245)
• No Mob Spawning on Trees (by oldjunyi)
• Hammer (Lib) Core (by Zeitheron)
• TombManyGraves 2 API (by M4thG33k)
• Waystones (by BlayTheNinth)
• TombManyPlugins - Cosmetic Armor Reworked (by M4thG33k)
• Rustic BOP Woods (by WolfieWaffle)
• Ding (by ohaiiChun)
• Rustic Thaumaturgy (by Voxel_Friend)
• Placebo (by Shadows_of_Fire)
• The One Probe (by McJty)
• Better Advancements (by way2muchnoise)
• SimpleHarvest (by TehNut)
• Thaumic Inventory Scanning (Thaumcraft Addon) (by BlayTheNinth)
• Pam's HarvestCraft (by pamharvestcraft)
• NetherEx (by LogicTechCorp)
• Animus (by TeamDman)
• PTRLib (by RazzleberryFox)
• FTB Backups (by LatvianModder)
• BiblioCraft (by Nuchaz)
• Chisel (by tterrag1098)
• JEI Integration (by SnowShock35)
• OfflineSkins (by LainMI)
• Chest Transporter (by cubex2)
• ConnectedTexturesMod (by tterrag1098)
• Crafting Tweaks (by BlayTheNinth)
• ArchitectureCraft - TridentMC Version (by darkevilmac)
• Mob Grinding Utils (by vadis365)
• Wolf Armor and Storage (by satyrnidae)
• RandomPatches Integration (by TheRandomLabs)
• Thaumcraft (by Azanor13)
• Villager Market (by face_of_cat)
• stimmedcow : NoMoreRecipeConflict (by GotoLink)
• Mantle (by mDiyo)
• Inventory Tweaks (by JimeoWan)
• Thaumic Additions: Reconstructed (by Zeitheron)
• Dense Metals (by knoxhack)
• Biomes O' Plenty (by Forstride)
• Controlling (by Jaredlll08)
• Thaumic JEI (by Buuz135)
• RandomTweaks (by TheRandomLabs)
• Blood Magic (by WayofTime)
• AttributeFix (by DarkhaxDev)
• Iron Backpacks (by gr8pefish)
• Mo' Villages (by TheWeatherPony)
• Hopper Ducts (by FyberOptic)
• FastWorkbench (by Shadows_of_Fire)
• VanillaFix (by Runemoro)
• TOP Addons (by DrManganese)
• AppleSkin (by squeek502)
• FTB Utilities (by LatvianModder)
• Fast Leaf Decay (by olafskiii)
• The Twilight Forest (by Benimatic)
• Just Enough Items (JEI) (by mezz)
• Baubles (by Azanor13)
• Iron Chests (by ProgWML6)
• BetterFps (by Guichaguri)
• Overloaded Armor Bar (by tfarecnim)
• LibraryEx (by LogicTechCorp)
• ReAuth (by TechnicianLP)
• Patchouli (by Vazkii)
• RandomPatches (by TheRandomLabs)
• Login Shield (by Glasspelican)
• The Aether II (by GildedGames)
• FTB Library (by LatvianModder)
• Blood Arsenal (by Arcaratus)
• Chameleon (by Texelsaur)
• Guide-API (by TehNut)
• Horse Tweaks (by BlayTheNinth)
• The Weirding Gadget (by AtomicBlom)
• Tomb Many Graves 2 (by M4thG33k)
• Rustic (by mangoose3039)
• Sophisticated wolves (by nightkosh)
• Mouse Tweaks (by YaLTeR)
• Storage Drawers (by Texelsaur)
• Chisels & Bits (by AlgorithmX2)
• Fancy Lamps (by a_frosted_one)
• Decocraft (by RazzleberryFox)
• JourneyMap (by techbrew)
• MalisisDoors (by Ordinastie)
• NetherPortalFix (by BlayTheNinth)
• MalisisCore (by Ordinastie)
• FoamFix​ (by asiekierka)
• Thaumcraft 6 Aspects for JEI (by zabi94)

Interesting, I'm not able to reproduce it with those mods. Could you post your logs?

That pack had Fancy Lamps on 1.1.0 installed, have you updated it to 1.2.1? If now I'll get those logs ready.

Do we have any idea what is causing this? I would like to be able to update without breaking all of thaumcraft

Can confirm the issue with 1.2 and above. Modlist below.
https://www.dropbox.com/s/dmkaz38rsummieu/modlist_20-11-2020_01-21-28.xls?dl=0