I have an update on this for whomever may be interested.
1. It took a while but mtnelectronics responded. They stated that it sounded like the 7135’s failed on all three drivers I have; 2 in 17mm and 1 is a 20mm. Identical mcu’s with the D4 V3 UI. We came to a full refund on two and a complete replacement for the third.
The replacement came a week ago and I did a test with it and it does function as it should.
2. Hoop helped me with a 17mm version of one of Del’s drivers with an attiny85 mcu. One of these…… DEL's OSH-Park driver boards. It does what I wanted. I may try building another 1 or 2.
7135’s are in a difficult supply situation and apparently there have been some bad ones. Mtn-E has had some issues with some but were very good to resolve the issue, just as they were in years past.
Now I just need to take the time to complete the project I have partially done.
I am finding it difficult to concentrate recently. One of the early season wildfires is nearing Los Alamos. Near enough to put the county into the “set” phase of the “ready-set-go” emergency evacuation stages.