Unfortunately theres not much history on MDWS to compare.
I'd be interested if you notice any change in latency.
I'd also be interested in seeing the VDSL2 framing parameters - Previous and current.
On the 'old' system all upstream lines had a low level of FEC protection applied by default - even if DLM wasnt taking any action to increase stability - and the RFEC was set at 16.
Its not impossible that one of these values related to RS such as the R/K/T/N have changed which could affect the amount of redundancy being applied... which in turn could affect the amount of recorded FECs.
MDWS doesnt (afaik) record these and you'd need to get them from the connection stats. We still arent certain of the relationship between the RS parameters -
linky.