Clean the purple colored Nd:YVO4 crystal with very pure acetone and see if your problem goes away. Do not clean the clear KTP crystal, acetone melts KTP under some circumstances.
I service ND:YAG for a living. We are not often surprised when the "crack" turns out to be the heat transfer material the crystal is mounted in. Otherwise your looking at 45-90$ for a new piece of Vandate.
Steve
Qui habet Christos, habet Vitam!
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