• Minecraft Version: 1.12.2
• BetterFps Version: 1.4.8
• Forge/LiteLoader Version (if any): Forge 14.23.5.2847
• Crash Logs (if any): N/A
• Other Mods (if any):
  -Abyssalcraft 1.9.12
  -Abyssalcraft Intergration 1.9.0
  -AE2 Stuff 0.7.0.4
  -Akashic Tome 1.12
  -AppleSkin 1.0.9
  -Applied Energistics 2 rv6-stable-7
  -Astral Sorcery 1.10.20
  -AutoRegLib 1.3
  -Baubles 1.5.2
  -BDLib 1.14.3.12
  -BetterFPS 1.4.8
  -Bibliocraft 2.4.5
  -Binnie Mods 2.5.1.188
  -Botania r1.10-362
  -Brandon's Core 2.4.17.208
  -Chisel 0.2.1.35
  -Clumps 3.1.2
  -CodeChickenLib 3.2.3.358 Universal
  -CoFH Core 4.6.3.27
  -CoFH World 1.3.1.8
  -CTM 0.3.3.22
  -Draconic Evolution 2.3.24.349
  -EnderCore 0.5.69
  -EnderIO 5.1.51
  -Ender Storage 2.4.6.137
  -ExtraUtils 1.9.9
  -Fast Leaf Decay v14
  -FoamFix 0.10.5
  -Forestry 5.8.2.394
  -Shadowfact's Forgelin 1.8.4
  -Fullscreen Windowed 1.6.0
  -Gravestone 1.10.3
  -Guide-API 2.1.8-63
  -Hwyla 1.8.2-B41
  -Industrial Foregoing 1.12.13-237
  -Infernal Mobs 1.12.2
  -Intergration Foregoing 1.9
  -Inventory Tweaks 1.63
  -Iron Chest 7.0.72.847
  -JEI 4.15.0.289
  -JEI Bees 0.9.0.5
  -Journeymap 5.5.5
  -JustEnoughResources 0.9.2.60
  -Magic Bees 3.1.10
  -Mantle 1.3.3.55
  -MatterOverdrive 0.7.1.0-Universal
  -Morpheus 3.5.106
  -Mouse Tweaks 2.10
  -Nuclearcraft 2.18j
  -OpenBlocks 1.8.1
  -OpenModsLib 0.12.2
  -Patchouli 1.0-20
  -PlusTiC 7.1.6.1
  -Railcraft 12.0.0
  -Redstone Flux 2.1.0.6-Universal
  -Tinkers Construct 2.12.0.157
  -TeslaCoreLib 1.0.15
  -Thaumcraft 6.1.BETA26
  -ThaumicJEI 1.6.0-27
  -ThermalDynamics 2.5.5.21
  -ThermalExpansion 5.5.4.43
  -ThermalFoundation 2.6.3.27
  -Tinker Tool Leveling 1.10
  -Twilight Forest 1.1.12
  -Unidict 1.12.2-2.9.2
  -Walia Harvestability 1.1.12
  -Wawla 2.5.273
  -bspkrsCore-universal-7.6.0.1
  -Treecapitator-Client 1.43.0
  -Waystones 4.0.72
  -Zerocore 0.1.2.8

Serverside Only;
InstantUnify 1.1.2

One of my players reported beacons not reapplying buffs when stood in certain areas of their base, tested with two seperate beacons in different locations and then tested on a singleplayer world in addition all with the same result.

Issue was rectified by disabling Fast Beacons server-side, posting this here for others with the same issue and for a potential fix in newer versions.