Heyo, if it's from a plugin/mod like Clear Lag, or another entity limiter, you'd have to check the configs. Make sure the server is off before doing any changes, and you should be able to find a config for the mod within either the home/container/config folder then the mod name, within home/container/(world name)/serverconfig and then the mod name, or if it's a plugin it'd be within the plugins folder (home/container/plugins) under it's name!
#Minecraft remove entity spawn limit
hard tendon
But base wise in Minecraft there really isn't a limiter.. which is why sometimes I find servers with like 300k items on the ground that crashes when someone joins 
lunar wind
okay i will have a look, i having issue with ATM9, its fresh server, fresh install, but when place armor stand it just deletes it straight away, no plugins or anything, ive reset the server chose different versions etc, but happening.... i try what u said now ty