Wallet doesn't sync: ERROR: invalid header received

### Describe the issue
Sync stopped at block 611036 even after restarting.
I tried invalidate/reconsider block commands on the problem block displayed in the debug.log file to no avail.
Please advise, thanks!

### Can you reliably reproduce the issue?
#### If so, please list the steps to reproduce below:
1. Start bitcoind using my conf file
2. doesn't sync past block 611036

### Expected behaviour
Finish syncing

### Actual behaviour
stuck at block 611036 and getting debug errors:
2020-01-03T03:29:45Z ERROR: AcceptBlockHeader: block 000000000000000000b48bb207faac5ac655c313e41ac909322eaa694f5bc5b1 is marked invalid
2020-01-03T03:29:45Z ERROR: invalid header received

### Screenshots.
If the issue is related to the GUI, screenshots can be added to this issue via drag & drop.

### What version of bitcoin-abc are you using?
0.20.9

### Machine specs:
- OS: Ubuntu

Start by reproducing the sync failure with bitcoind using the reporter's conf file and inspect debug.log around block 611036, especially the AcceptBlockHeader and invalid-header messages. Done means determining why the block is marked invalid and restoring synchronization past that block, with a regression test if the relevant test location is found.

Written by the indexing model from the issue text.