Time machine backup to Time Capsule woes


My wife and I backup our MacBooks to a single Time Capsule via WiFi. We have been doing this for several years without an issue. A few days ago my computer began to report failure because “the backup disk image could not be created”. My wife’s computer continues to backup as always.

The Time Capsule has 1.4 of 2 TB available. I have rebooted both the Time Capsule (and WiFi) and my MacBook. The error continues. I also backup to a directly connected external hard drive alternately and this has continued to work. I have deleted my sparse bundle on the Time Capsule and attempted to start afresh. No good.

I can’t find this problem mentioned in online forums as people sometimes get the error message from the first time they set it up - but not apparently after it has been working for years.

Any suggestions please?