re: Thornless blackberries not ripening

Too much water can evidence conditions similar to too little water, as the actual problem is lack of soil oxygen available to the plant.
I have a similar issue with my blackberries this year. Made fruit that were not fully formed and then were so slow to ripen some fruit are drying on the bush.
I attributed mine to not enough sun/light/day length. I moved them to a sunnier spot in the garden but don’t know if it will help next year.