1998 Volvo V70 2.5T SE 5.8V on Crank slow start

[Lperry363]

Hi guys, I’ve been having some starting issues with my 2.5T SE. Earlier in the year I changed the ECT and it seemed to fix everything. That was long crank and overfueling but fine once warm. Fast forward a few months and the long crank is back but no overfueling and fine right after starting. The battery drops to 5.8v on crank for a millisecond. I thought crank position sensor but this would play up with low voltage so could be fine? It also starts fine the 2nd, 3rd time etc. voltage is fine on idle and driving. I cleaned up the battery terminals but no change. Battery is 1.5 years old Bosch. Any ideas? Thanks