It’s also not a good time of year to oversow a cover crop as germination will be poor (seeds dry off quickly in dry warm weather). E March or E September are the best times.
If you sowed in Sepember and overwintered cover crop, this would affect species you can use as most legumes will not tolerate much flooding.
Soil pH will also affect what species that will work well.
Vole population is cyclic over a period of 4-6 years. We just had a peak vole winter and damage to various woody plants. Maybe yours is peaking too. The only good thing about that is that population will crash via predators having a feast this year!
You could sow a cover crop in September and start planting out in the winter as well, allowing cover crop to remain for a year or more.