Today the same problem started to happen on another VPS server. So we cannot use gateway anymore on any server.Gateway hansa.log says:
2019-08-03 19:55:52 database cache may be max 80% of physical RAM (physical RAM is: 0 bytes, attempted to use: 100000 bytes for DB cache)

But we have free memory:
free -m
total used free shared buff/cache available
Mem: 4096 473 2265 128 1357 3432

CentOS Linux 7.5.1804

Kernel Linux 2.6.32-042stab138.1 on x86_64


I believe this is a bug.