After serious thinking Martin Brown wrote :
I blame lack of mechanical sympathy for your woes.

Or it could just be very tough grass and never throughly dries out. We
have a few inches of soil, under which is very heavy clay. It used to
flood in heavy rain, but I put in lots of drainage to try to help
prevent it. It usually needs a week of dry warm weather, even in the
summer, before it is fit to try to cut it - so sometimes it just has to
be left uncut. The first cut of 2018 was very delayed by the wet
weather.