[flybouy]

I would suggest not using it until you have time to investigate or replace it. Amplifiers don't like sending out power without a load. The only way to safely do that would be installing a resistor to absorb the load. Your head unit should have a switch to turn the front speakers off "'A" and still use the back "B". Speakers.
The speakers are typically attached to the wires by crimp on spade lugs. Seems to me the logical move would be turn off the "A" speakers until you can order or stop by Wal-Mart and get replacements. You will be doing the same amount of work and time to "tape off the wires" as you would to replace the speakers. Replace both speakers on the front or rear so the amplifier has a balanced load.
Don't be surprised if you replace the speakers and still have the issue. The head units (radio) in RVs are notoriously inferior units and may be defective. The only way to know would be swap the left and right speakers and see if the problem follows the speaker. In my opinion, the money to buy replacement speakers wouldn't be wasted if is the head unit is defective as the speakers that come in most campers are junk. JMHO YMMV