Observation: Same PIC works on one board but not another.
Axiom: The problem is caused by some difference between the boards.
Thinks: just what are the differences?
If you can't deduce the problem, test it by experiment.
Change the circuit or components step by step until the iffy board
should be exactly like the good one.
At some point, the offending difference should disappear.

What is your app, so we have an idea of how complex it is.

Problems I have met:
People giving me boards with wrong crystal values.
Code not initialising variables to zero
(this reduces the number of random start-up states)
Floating inputs not properly pulled up
(found when debugging an 80C188 design!)
The crystals may be the same frequency, but are they the same cut/mode?
(32.768 xtals are meant to run in Low Power oscillators -
maybe one has be over driven and damaged and ticking erratically)
Try it without the LCD.

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