Apr  9 10:14:46 hostname kernel: zram: Decompression failed! err=-22, page=337905
Apr  9 10:14:46 hostname kernel: zram: Decompression failed! err=-22, page=337905
Apr  9 10:14:46 hostname kernel: Read-error on swap-device (251:1:2703240)

Many more errors like this have been logged. I did use zram with the default lzo for a long time now without errors. Shortly before this error occured, I switches to lz4hc (and at 10:14 the system got under high memory stress causing one process after the other to SIGBUS away).

Don't know if it's important, some system infos:

processor       : 5
vendor_id       : AuthenticAMD
cpu family      : 21
model           : 2
model name      : AMD FX(tm)-6350 Six-Core Processor
stepping        : 0
microcode       : 0x600081c
cpu MHz         : 1400.000
cache size      : 2048 KB
physical id     : 0
siblings        : 6
core id         : 5
cpu cores       : 3
apicid          : 21
initial apicid  : 5
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf eagerfpu pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb cpb hw_pstate vmmcall bmi1 arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold
bugs            : fxsave_leak sysret_ss_attrs null_seg
bogomips        : 7798.83
TLB size        : 1536 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro

gcc (Gentoo 5.3.0 p1.0, pie-0.6.5) 5.3.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.