Corrected entry: Early in the movie when the parents are digging up the enemy robots, the arms that are sticking out of the ground don't belong to either of the two bug bots that are used in the later fight.
ZeroVey
22nd Mar 2012
Mighty Morphin Power Rangers: The Movie (1995)
Correction: Actually, the "arm" you refer to is part of the back leg and foot of the scorpion zord.
Correction: So Ooze had three robots and one of them didn't work after so many years buried.
LorgSkyegon
There is no evidence anywhere in the film that there is a third, inoperable robot. Ooze even says, "the other one must be close" indicating there are only two.