MacOS Sierra / Numbers 4.0: Problem with saving on a Synology via AFP

I updated my Mac to 10.12 Sierra and updated Pages, Numbers and Keynote afterwards to the latest versions.

So far so good, everything running normal.

But unfortunately saving a Numbers file via AFP on a local Synology NAS (DS1815+, latest DSM) caused the application to crash and kicked all connections to shared folders.

Saving on the local HDD is no problem at all.

Then I tried to figure out whether thats a single problem with AFP and killed the AFP file service on the NAS to only start the SMB2 service.

No problem to save on the NAS via SMB.

I tried to save a numbers document on the NAS via AFP from another Mac. This time with an older version of numbers (3.6.2) but on a freshly updated macOS Sierra and it causes the same crash of numbers and all connections to the NAS.

Therefore:
It seems to be a problem with macOS Sierra and the AFP server of the current Synology DSM (6.0.2-8451 Update 1).

Is anyone experiencing the same issues?
Does anyone have a suggestion for a workaround?

Thanks a lot.

Edit:

I think it might be a problem with the versioning of the applications which use file versioning. Someone described the same behavior with Preview while saving a JPG image. And I could reproduce the same crash with my Macs.