why do the spool skips and lets all the line go? There is little resistance on the spool to keep the line in. I do not even press the spool on the ground to allow more line out. It does it all by itself. Is there an adjustment that needs to be made or do I need to replace the spool? The trimmer is Craftsman 13" 4.0 AMPS Trimmer Model 358-745290. I appreciate your help on this. Evaristo.