Do you think his visit with his mum could've evoked memories/thoughts of his dad? My Hs dad died one year after we M (almost to the day) and even now 19 years on he still struggles with this fact (I'm convinced it is the reason for his MLC).
Try not to worry too much Holly (easier said than done I know)
Me 43 XH 45 M 2.7.88 Divorce 7.10.09 Kids D20,S17 & D15