[hanspeter]

I'm not a programmer, but doesn't this smell like the GPU thinks the 16MB is still hers, and as soon as it's used by the OS, kaboom?

There are hundreds of users of these builds. I think an issue like that would be hit by more than one user.
Note linux uses all free memory for file caching, so even if kodi isn't using all memory, it will after a while all contain important data.

It seems something is unusual with your hardware or configuration.

Can you detect the problem more quickly with this:

Code:

wget https://www.dropbox.com/s/z6twfxt63vchcio/memtester?dl=0 -O memtester
chmod +x memtester
systemctl stop kodi
./memtester 512M

(use a higher size than 512M if that doesn't spot a problem)

Can you test a fresh install and see if that still has crashes for you? (Don't adjust config.txt or install any extras).
If it does, there may be a hardware problem. If it doesn't then something you have configured/installed has caused it and it would be good to identify what.

the memchecker seems to run fine with up and including 628M. With 629M, it freezes after a few Stuck-Adress-Loops:

Code:

./memtester 629M
memtester version 4.3.0 (32-bit)
Copyright (C) 2001-2012 Charles Cazabon.
Licensed under the GNU General Public License version 2 (only).

pagesize is 4096
pagesizemask is 0xfffff000
want 629MB (659554304 bytes)
got  629MB (659554304 bytes), trying mlock ...locked.
Loop 1:
  Stuck Address       : testing   4

With 630M, it freezes immediatly on the first loop:

Code:

./memtester 630M
memtester version 4.3.0 (32-bit)
Copyright (C) 2001-2012 Charles Cazabon.
Licensed under the GNU General Public License version 2 (only).

pagesize is 4096
pagesizemask is 0xfffff000
want 630MB (660602880 bytes)
got  630MB (660602880 bytes), trying mlock ...locked.
Loop 1:
  Stuck Address       : setting   0

does this mean anything...?