For me, the problem started 2016-December-05, under Mac OS X Yosemite (10.10), with my 3 year old 3 TB Timecapsule:
in German: ", muss Time Machine ein neues Backup für dich erstellen. "
(in English: "… Time Machine must create a new backup for you." )
The message reappeared in 2017-January, whereup I connected a firewire disk for Time Machine.
On 2017-January-15 my Mac failed (graphics board), I had to buy a new Mac.
The new iMac under macOS Sierra (Version 10.12.2) used the existing TimeCapsule for five days. Today it came up with the usual …must create a new backup….
… Yosemite does not have this issue, so it seems to be a bug in Sierra.
I conclude: the problem exists with MacOS Yosemite and with Sierra.😟
I called Apple support, the friendly supporter did not find any useful information, just old stuff.
⚠Apple, find a solution. Please, do that fast!⚠