Hi @aimar, My E4.5 ubuntu edition (purchased new, July 2015) is misbehaving since OTA-10 (stable) also. It crashed once so badly I thought it would never start again! Long hold of power and vol buttons worked eventually. However it seems to have a settled down a bit now. But I am considering a fresh install.
The apps I mainly use are Dekko, Messaging, Teleports and Browser. Browser is fine. Dekko mostly ok but notifications sometimes not happening until app is opened. Messaging has been weird with flickering sometimes, sent message remaining in the input box after message sent. I don't use it much but I think it has got better recently. Teleports notifications sometimes don't happen until app opened.
The wi-fi icon on the top notification bar (what's it called!) often goes blank whilst on the pull down settings the router is shown as selected and showing strong signal. Tapping it will bring the icon back.
I guess the wi-fi and notifications issues are linked. The phone has always been sluggish connecting to wi-fi and going into airplane mode. Slow also to re-connect to wi-fi after being out of range...I usually have to give it a nudge. My Nexus 7 switches almost instantly.
I wonder about the lifespan of this device and all similar devices. It might be nearing end of life. But I'll stay with it (hopefully) until something better turns up to run ubtouch on.