You are seeing the precursor to thermal runaway. I am not too worried because you are micromanaging the charging process, not a 19 cent IC chip. But when the amperage starts ramping up again the battery gets interested in heating up.
IMHO forces are at work. You are being forced to force feed the battery to get it to act normal. It's going to be interesting to see length of service values when all is said and done. A reluctant 2-volt cell has really thick plates to fall back on. But we have to see how you and your 31 fare. BTW, BCI group 29, 30, and 31 are fraternal triplets.