Reset circuit loops forever on-off
Having a PIC reset itself by pulling the rug out from under its own feet is a risky move. I'd suggest that you monitor with a scope a couple of points. Firstly, is the VCC_IN dipping when the relay turns off and reconnects the VCC_OUT (and charges the caps on the rest of the board)? That could cause the TR input to drop because of the R405/R406 divider, while the upper third point connected to CV may hold up better due to C403 - that'll depend on the value of the internal divider resistors.

Secondly is the behavior of the PIC. After reset the pins default to inputs until the TRIS registers are set, so they'll appear open, allowing C405 to charge, then they'll set to an unknown state - but probably low, until your code sets it high for normal operation. The timing of this may generate the edge at TR that causes the 555 to re-initiate.