Both downstream and upstream are exhibiting excessive noise, in particular interference due to 4G/5G ingress. Channels that overlap with 4G/5G frequencies show low MER values and high amounts of (un)correctable codewords. As a result of the noise/interference, the modem is continuously resetting the cable interface to re-establish connection to the CMTS (T3/T4 timeouts). As indicated by the 'RCS partial service' messages, one or more of the 24 DS channels become unusable from time to time.
Please connect the modem cable directly to the AOP (main coax socket), even if it makes no apparent difference. The splitter is redundant, causes excess attenuation and makes the modem even more vulnerable to noise ingress.
The modem should ideally be connected using a 1.5-meter IEC/F cable (see picture below). You are using a custom-made cable at the moment. What is its estimated length? Are the modem and router located in separate rooms?
Furthermore, I have noticed that a white (indoor) cable is feeding the AOP. Normally, this is a green (outdoor) cable. This would mean that the green cable was once extended.