To resolve the disconnection problems I migrated mekk.waw.pl to another Linode datacenter, now it is operating from London. So far it seems that it helped, not a single disconnection during first day of work (while from Newark there were a few connection breaks an hour).
Big thanks to people who performed the tests I asked for (especially those who confirmed that connections from London Linodes are working properly).
There were usual DNS issues today, they also seem to be gone.
Incomplete and interrupted games played during last 3 months remain in the database, unfortunately I am not sure whether I will have time to correct them, although I still consider doing it.
In case you happened to play particularly important game, which you would like to embed or link to, but which is spoiled, let me know (preferably by email), I will patch it manually.