Okay, now we are getting somewhere.
You’re using shared memory to communicate information between two programs, this is ill advised. The jumps you are experiencing may be the result of thread lock, which is common among shared memory situations. The game thread of Unreal is waiting on a memory region to be released by the other program so that it can create the mesh section. It’s much more advisable that if you must communicate between two different programs, you do so through an appropriate communication layer, TCP will do in a pinch. The difference will be that while it might be slightly slower, there will be far fewer chances for the race conditions you may be experiencing.
As for the old meshes, garbage collection will take care of any left over memory allocations made for them, if you’re only making approximately 60 meshes a second, i don’t think garbage collection lag is the issue.