This has been reported sporadically over the years, but I've never been able to replicate it. I just set up a tournament with 16 players, and 2 tables of 10. Locked someone at table 2 and busted players out of table 1 until the correct balancing action was to move someone from table 2 to table 1. The TD suggested one of the unlocked players. I canceled the move and press the Suggest Movement button. The TD suggested someone else, another unlocked player. I repeated this over and over until I was pretty sure every player at the table had been suggested for movement several times, except for the locked player. The TD never suggested he move.
A Locked player is not a guarantee that a player won't be moved. An obvious scenario is when a table needs to be broken down. If that table has a locked player, the player's going to be moved. The TD won't suggest moving a larger group of players from another table that doesn't have any locked players just to avoid moving even one locked player. There are probably others scenarios, I just can't think of any at the moment. (I just tried a dealer button scenario, but even then, when the obvious choice for a player to be moved is a locked player, the TD will randomly choose someone else to avoid moving the locked player.)
If you run across this again, I'd love to see it. Save the tournament and make a copy of that saved tournament file and then continue with the tournament. Then send that copy to me when you get a chance. I'll see what I can find.