Does it happen less in Windows safe mode? https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Unfortunatlu it's hard to run Windows safe mode for a long time (longer then 1 hour) in our company to see if it helps. :( I've try to run thunderbird safe mode and reset to default and add Thunderbird to exceptions in ESET but it didn't help.

These are some generic suggestions to avoid problems with anti-virus software.

Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_how-to-find-your-profile

Don't let your anti-virus software scan incoming and outgoing messages.

Don't let your anti-virus software scan attachments.

Don't let your anti-virus software intercept your secure connection to the server.

Remove any add-ons your anti-virus software may have installed in Thunderbird.

Keep it working. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

And last but not least, backup your Thunderbird profile on a regular basis. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

Additionally, https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems