If the issue happen suddently without software upgrade, I can suppose It can come from a problem in database even I don’t see what it can be.
So have you tried an old zigbee network backup (the backup/restore feature visible in Phoscon) ?
All your system is on SD card, deconz is on the same one than HA ?
How many devices have you ? Can try to make a backup and restart fron scratch with only somes devices to make tests.
But take care some sensors can leave the network if they are without parent for long times (somes hours)