I added
$wgMainCacheType = CACHE_ACCEL;
$wgSessionCacheType = CACHE_DB;

which did not help then I realised I already had

## Shared memory settings
$wgMainCacheType = CACHE_NONE;
$wgMemCachedServers = array();

CACHE_NONE is recommended above. I tried both ACCEL and NONE.
I deleted cookies. I don't know how to access the database. I still can't log in on one browser (my main browser) but I can see the wiki content.