pgitta,
Hard to say exactly what is causing your problems but you may want to take a gander at the following info before you sell another transmitter with the wrong crystal.
Special Notice about Frequency Changes-
*72MHz- Low band channels 11 to 35; High band channels 36 to 60.
Receiver crystal channels (11-35 or 36-60) Within Each Band
Can Be Changed, and Do Not Require a retuning of the receiver.
*72MHz Frequency Band (low or high) for the receiver Can Not Be
Changed from low to high band, OR from high to low band without
sending it into Futaba Services for retuning.
*50MHz, 72MHz, 27MHz and 75MHz Frequency Bands Can Not under any
circumstances be interchanged with each other. 72/75:receiver Must
be sent in for retuning to the appropriate band. 50/27: can't do.
*50MHz, 27MHz and 75MHz receiver crystals Can be changed anywhere
within the respective bands. There are no high or low bands such
as the 72MHz band has.
*Transmitter Crystals Can Not be changed to another channel except
by a licensed service center. It is against FCC regulations, and
illegal for the user to change a frequency determining component
of a transmitter. If the radio is not retuned, it can be a hazard
spectators, modelers or property, and void AMA insurance coverage.
*Check with the local R/C club for the frequencies used in your area.