The old 8v 1.5TDCi was generally quite a stout engine.
I did have a 2015 Focus 1.5TDCi that seemed to suffer with issues regarding keeping diesel out of it's sump during DPF regens. I think it was the reason I joined this site in the first place. I then had a 2016 Focus 1.5TDCi that didn't suffer with this issue at all and was also a lot nicer to drive. Weird, as they were both 120ps models.
I believe the later 1.5TDCi's started using the PSA 16v head. There is an issue regarding them using 7mm chains between the cams that wear out prematurely and snap. I believe they give an awful lot of warning before they fail though. The chain was later revised to an 8mm unit which should be more durable.