Low EPQ instance bug on stage 3/4

Description of the bug: (optional screenshot/video):
Uploaded the pictures since it bugged out copy paste
What is supposed to happen?: one instance of the map mobs not different
Where did you find and/or notice this bug?:EPQ afk on alt on stage 3 and spawning in after mob are gone or half gone then there are new frozen/idle spawned on alt and when you hit them they move and eventually spawn for others
A step-by-step guide to re-producing this bug (optional):
on alt on stage 3 and spawning in stage 4 after mob are gone or half gone they still spawn new frozen mobs on alt and when you hit them they move and eventually spawn for others
Extra information (optional):
Could be an issue with the server lagging, idle mobs could cause a weird memory leak?.
Normally whole party spawn into instance but since update everyone spawns in randomly

 

On image 1 got 25 marbles also max should be 20