Mutt losing folders with new mails with additional session

[mike9 at posteo.nl]

Hi,

My issue seems to be similar to this:
http://lists.mutt.org/pipermail/mutt-users/Week-of-Mon-20200106/001471.html

I'm running procmail and mbox folders on Gentoo. mutt-1.10.1 works fine.

When using mutt 1.13.5 or 1.14.4-r1 opening an additional session makes the
first session forget about folders with new mails.

Example:
- Folder a defined by 'mailboxes' command
- Start 'mutt -y' (session 1), switch to foder x
- Incoming mail in folder a,
  1.14.4-r1 shows new mail notice for folder a at once,
  1.10.1 shows new mail notice for folder a after key press (e.g. some
  cursor key)
- Hitting 'c' suggests switching to folder a, abort by Ctrl-g
- Start additional 'mutt -y' session.
  When running 1.10.1 session 2 shows 'N' flag for newest folder a but
  1.14.4-r1 does not
- Hitting 'c' in session 1 again (1.14.4-r1) does not suggest any folder
  anymore, 1.10.1 still does

Don't know if this is important: Without having changed the use flags
manually the ebuilds' IUSE variables of 1.14.4-r1 and 1.10.1 differ:
< autocrypt
> crypt
> gpg
> nntp
> notmuch
> smime

Any idea what causes the first session to forget about the folder
with new mail in versions >1.10.1?

Thank you.

Mike