I did have zswap enabled for a long while, and a lot of wine games, plasmashell, xorg, kwin_x11 (and other) did crash randomly when reached 100% of physical ram and swap was like almost never used.
I could esilly open a lot of browser tabs and the browser or xorg would fail every time.
After disabling zswap no crashes at all.
zswap_compressor=lz4 # lzo lz4
zswap_max_pool_percent=25 # 1-99
zswap_zpool=zbud # zbud z3fold
I have just figured out independently that zswap was causing random crashes for me as well (and that's how I found this bug). It had started somewhat recently, as I've been using zswap for quite a long time and crashes started appearing only somewhere in the last two months or so. At one point I've suspected hardware failure, but thankfully, it was still crashing when run on another PC :P
Every day I would find bunch of segfaults reported in dmesg, usually some background services, but occasionally taking down my browser, desktop or even complete X session. Now with zswap disabled it runs for the third day without a single segfault; however, as I have only 8GB RAM, the lack of zswap is somewhat noticeable.