Sub-carrier number 453 is centred upon a frequency of 1.95 MHz. In what band plan does that frequency fall? Ah, yes. We've been here before, it's the Amateur Radio "top band" (1.81 - 2.00 MHz). So my suspicion is that it is a licensed transmission or beacon in that frequency band.
How have you proved that signal was the reason for your circuit's re-train? Surely it is just a mere co-incidence? To prove that it causes your circuit to re-train, you need to know the source of that signal and, with the co-operation of the person responsible, arrange to have it turned off and then back on again. If, after a repeated sequences of the above, you see that every time the signal appears your circuit re-trains then you can claim proof.
To avoid circuit re-trains you will need to increase the target SNRM. Try with it set to 2 dB.