Something wrong with grenade trap buff

first of all i look back again on the old versus.
im not really sure it's new or old bug, because since it get nerfed long ago, many people dont use this buff anymore in versus include me.
if im not mistaken, its get nerfed because some people in vs say this buff is too overpowered, but they said the infected is too overpowered also. so if the infected is too OP also, why grenade trap get nerfed with the 3 traps limitation? that will make the surv weaker.
both surv and inf are too OP should means balance... i still don't get it which that really too OP. for me, if talk about gameplay+strat, people will never end to say "too overpowered". except like why veteran pistol get nerfed, yes this one is really OP.

if can't make the buff back like before without limitation but please fix this one
It says,
"Limitation : You can only leave up to 3 traps at the same time and can only create 3 traps of each type per round."

i think its like 3 pipe, 3 molo, 3 bile per round/stage and only 3 traps max on same time. CMIIW

now i use this buff again in coop, in one campaign i put 3 traps (pipe bomb) before final, then on the final i can't setup the pipe bomb. then i thought maybe it's 3 traps max for 1 campaign.
on the next campaign i still can't setup the pipe bomb, but i can setup molotov, but it says something like "(2/3) for this type" even that is my first trap in that campaign.
on the next next campaign i can't setup any trap like pipe and molotov (i didn't try the bile bomb).
so i can't setup the trap again till i rejoin the game..
I don't Know this is only me or equip and unequip buff will affect this too, but please check and fix if there is really a bug. thanks