Fix thread safety issues

[Kamillaova]

Example:

Time 1: Thread 1 writes holograms - 30% Thread 2 writes holograms - 20% - ☠️ Thread 3 reads broken holograms - ☠️

Time 2: Thread 1 writes 31-40% of holograms Thread 2 writes 21-100% of holograms - ☠️☠️☠️

Result: Totally broken holograms file and many errors Also holograms.yml is completely erased after a failure like this

[OliverSchlueter]

Thank you!