U2414H, input timing not supported (in daisy chain)

Since a few days ago I get the well known "The current input timing is not supported by the monitor display. Please change yout input timing to 1920x1080, 60 Hz or any other monitor listed timing as per the monitor specifications". I am using an DELL XPS 13 9360 an have two daisy chained DELL monitors. The connection is:
DELL XPS 13 -> USB-C/DisplayPort adapter -> DisplayPort/Mini DisplayPort cable -> DELL UP2716D -> DisplayPort/Mini DisplayPort cable -> Dell U2414H
The error only occurs on the U2414H, so on the last monitor in the chain, not on the UP2716D. This setup worked fine without any bugs for about a year or so.

What I did to resolve the issue:

- used other cables

- used another cable configuration with HDMI

- reset the U2414H to factory settings

- unplugged all cables, including DP, MiniDP, USB and power and 'drained' the monitors

- change the settings of the first monitor to 1920x1080, 60Hz

- updated all graphics drivers

- reinstalled all graphics driversand maybe some things more I can't remember in the moment.

Are there any ideas I haven't tried yet?