An additional signature is appended to a draft mail each time it is accessed for editing

Expected behavior

Only one signature text block should be appended to a new message

Actual behavior

An additional signature is added to a draft mail each time the draft mail is accessed (i.e. for editing purposes). The additional signatures each have an additional empty line between their original lines.

See example below where two additional (and flawed) signatures had been added when accessing the e-mail draft two times. The last of the three signatures is the original one and it's fine. The two signatures above are flawed by additional lines and should not be there at all.

Example:

--

Peter Mustermann

Mustermanngasse 3

99887 Musterstadt

--

Peter Mustermann

Mustermanngasse 3

99887 Musterstadt

--

Peter Mustermann
Mustermanngasse 3
99887 Musterstadt

Mail app

1.7.2

Mailserver or service:
sprit.org

Server configuration

Debian 10.3, Apache 2.38, MariaDb 10.3.27, PHP 7.4.13, NC 20.0.4

Client configuration

Firefox 84, Ubuntu 20.04.1 LTS

No source file, test, or entry point is identified in the issue. Reproduce the problem in Mail 1.7.2 by opening the same draft for editing repeatedly, then trace the draft-editing and signature-handling code and verify that reopening the draft leaves only one signature block.