Slow post uploading procedure in file manager

Hi. Here is the problem

So… This is not first time, when impossible to upload fast to hestiaCP server via file manager a file (archive for example).

The procedure of uploading → pretty fast.
But procedure of saving data to disk → extremely slow, and takes up to 100% CPU for several minutes for 300MB zip archive.

This is not okay.
Can you please test and check what is going on?

Technical information:
ubuntu 20.04
Vultr
1GB RAM, 25GB SSD, 2GB SWAP
HestiaCP 1.4.7
Default installation (with apache, etc).