A patch or two ago ED fixed a years-long bug/incorrect implementation of TWS and now made it so when you enter it, it will automatically start tracking your highest priority trackfile on the display.
THIS IS THE INTENDED AND CORRECT BEHAVIOR
When you designate (or "bug") something in TWS, it is not locking the target aircraft. If its a client aircraft, they will NOT get RWR spike indications. Only Single-Target-Track (STT) mode will trigger the RWR, or when the AIM-120 goes active on them.
If there are no bandits and only friendlies, then it will track the closest friendly. This is fine. As I understand it, pilots in the real thing use TWS bugging to keep SA of lead and wingmen in shitty visibility conditions, as well as forming up on tankers.
Again, the display will always attempt to track something. If you want a clear radar and clear HUD, switch to RWS and select ERASE at the top of the RWS display if lock still isn't broken.