Better and a lot cheaper to locate the source of the glitch. If your engine has a mag, (yours does not since you noted engine battery) make sure it's properly grounded and you're using the correct plug. If you have an ignition with a grounding strap, relocate the end of the strap to the cylinder head by drilling a small hole in the top fin and affixing the strap with a screw and nut. Likely you have it attached to the mounting plate on the back of the engine. That's very often a poor ground. Again, use the correct plug. Resistor type plugs in both cases, one with an "R" in the part number.

Next clean all the servo and extension connectors to remove any tarnish that may be there. Next use a piece of tape to secure the crystal in the end of the receiver. Did you use an old, previously used switch? Replace it (them?) with new. Now make sure the ignition battery has a full charge on it. A low ignition battery can cause glitching, and of course rough engine running. Check the landing gear mounting screws to see if they are tight and secure. Use Locktite to assure they remain secure.