Devices drop off but still work (well sort of)

I’m using Zigbee2MQTT and most of the time everything is fine. However, from time to time I get some devices (not predictable which ones but normally bulbs) that report as offline. If i try to control them individually then nothing happens, they won’t respond. If they are part of a group and I control the group then they will respond correctly.
They never come back online of their own accord although a power cycle will get them back online.
Anyone encountered this sort of issue ?