Not only that but changing a crystal without retuning the associated chokes, can cause serious sideband and overtone issues.

I've the recipient a radio hits caused by an idiot who elected to change his crystal, destroying my plane!

The guy erroneously assumed that he could merely swap out crystals...

I had a plane on a different frequency which had always been rock solid reliable.

I was making circuits of the airfield, and noticed a glitch as my plane went by his station.

I didn't think of it at the time... on the next pass my plane went in when it went by his station...

After the crash I pulled out a frequency checker I picked up that has an LCD display that shows overtones and spikes...

Sure enough his TX was producing a spike on my channel.

When the guy put his original crystal back in, the spikes disappeared on other channels.

I told him he owed me a new plane...

He never returned, never offered to pay, and is no longer a club member.... good riddance!