Sorry that I missed your thread. I usually watch for such threads, subscribe, then try to help if I can.
In the other thread you referenced, you said all is well now. So, I figured it would be good to be clear here, that you chose a 3TB WD AV-GP drive, and even though it shouldn't draw more than the stock 500GB drive (not a very efficient stock drive), you achieved better operation after upgrading from the wimpy Roamio 12V 2.0A wall-wart (12V 2.5A bricks seem to be the ideal choice).
My experiences were similar, using 3TB WD Red Nas v2.0 WD30EFRX drives. The system information screen took minutes to populate, along with issues like you describe.
It turned out that some sectors, located in operationally critical areas, were unable to be read, but were not getting flagged by the drive, SMART, or the TiVo OS. The long road to fixing it, included overwriting the whole drive with zeroes, and finding that the sectors were not reallocated (reclaimed, instead), as they wrote fine, and then read fine, taking them off the Raw Read Error Rate SMART value, which only registered the errors when connected to a PC and a read test was run, followed by write zeroes, then a full read test. After all that, the SMART attribute values finally reflect what they should. This left me certain that the sectors with issues were "weak writes", which was telemark's suggestion, to explain what seemed impossible to many (the sectors being physically OK, and reclaimed, without reallocation/remapping of sectors).
The working theory was the power supply not being up to the job, and affecting the strength of the writes to those sectors. I also found what I believe to be an indication that drives with TLER/ERC (RAID/NAS drives), will tend to make it harder to know the status of the hard drive, as they use 7-second Time Limited Error Recovery, moving on, after 7 seconds of trying a sector operation, rather than keep working at it. (I'll clip these details here.)
In the end, I swapped all my 12V 2.5A LiteOn power bricks for my Cisco STA1520 tuning adapters (TAs), with my 12V 2.0A Roamio wall-warts (reversing the roles). Everything has been noticeably more stable, since the change, and even the SDV duties the TAs handle, now using the Roamio warts for the TAs, seem better (I'm sure it's on the TiVo side of the equation).
Cisco tuning adapters should never be used inline (using the TA coax OUT port) to connect a TiVo, if MoCA is in use. Use a splitter w/PoE filter on leg to TA, use other leg for the TiVo. Enjoy!