I haven't an answer for you - just wanted to make the observation; having voltage on a test point is no guarantee current is flowing through the circuit and for current to flow, at the other end of the circuit there must be a return, ground path or whatever.
There is a trend these days for power to be supplied to one end of a circuit and the switching or control elements to be at the other end. Commercial circuits are devious and it takes a fair amount of skill to test them and obtain meaningful results.
One problem a person has with testing a tv that is as much computer as tv, is many circuits have a level of intelligence for self protection - they sort of know if they aren't working right and can shut down. Modern thinking seems to be any lengths to prevent fire...
The Toshiba DVR620KU does not support dual-layer discs. See this page from ManualsLib, https://www.manualslib.com/manual/203807/Toshiba-Dvr620ku.html?page=9#manual . There is also a list of known compatible DVD discs for use with the recording function of the DVD rewriter/VCR on the next page. You should be able to dub a 2 hour (120 minute) tape to a DVD+R (4.7GB) disc. (I'll assume there is no copy protection on the tape.)
Look at page 50 and 51 for the directions for dubbing. Page 50 is here https://www.manualslib.com/manual/203807/Toshiba-Dvr620ku.html?page=50#manual . You'll want to focus on the directions in the left column. Note the section about auto-tracking of the VCR tape. Make sure to correctly indicate that the VCR is the source. Then after dubbing, finalize your disc to watch it on other DVD players.
I hope this helps.
Cindy Wells
If this set has video board it may be the culprit. Some sets video board and control board are combined. So you may have to do some searching on google to find others who have had similar failure and solutions.