I dont know about IRL, but In game, I dont think so. But. In the clip you shared (in the F-4) you look right and see the missile coming at you as it has a marker in ARB and you can see its rapidly approaching, in that situation I would have immediately dumped 4 or 5 chaff and then pressed chaff again every 1 second or so (maybe even 2 chaff every second). The closure rate means that the missile would like hit or miss within a few seconds, which it did. You will also know when the missile is defeated by chaff because your RWR should stop screaming at you.
One of the biggest thigns to impact whether or not you can lock on is ground clutter. If the target is too low to the ground, then a normal search radar might not be able to find it in the all the noise.
PD radars can find targets within the noise but are dependent on the target moving towards you. Only some radars are good enough to lock on to a target in moving away from you and PD radars dont work for targets moving left/right relative to you.
So If I would hazard a guess. The issue is that the radar simply cant find the target. But next time it happens, share a clip and I’ll see if I can identify the specific reason in that case why the radar couldnt lock.
Yeah… In game or online, guides dont cover everything. I’ve more than a few times submitted a clip and asked for help and gotten some really in depth detailed explanations as to why something did what it did and without that explanation, it looks like a bug. You could probably get a masters degree in War Thunder radars and still not have a clue what is going on half the time.