Many car relays are 20a Resistive load, ~ 10a for motors.
HL Motors draw ~ 4a normally and well under the limits.
If you burn the relays repeatedly, Dirt likely isn't your problem.
Motor winding on the armature and more very likely has burn damage too and may not be easy to see for nubes.
While many know about Gen1 Motor "twitch" when Off killing the battery...
Can have same problem when doors are Up but won't be obvious because won't kill the battery. Will Still cook the HL motors.
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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave