Our washing machine was stopping at various stages

Our washing machine was stopping at various stages & would beep and just not continue with the cycle. (Sometimes it would fun a full cycle without a problem however). We took it to an official repairer who installed a new sensor. We managed to do 2 loads when we got it home, but the third load must have been a little unbalanced. The machine started to move around. When we got to the machine the lid was obviously locked because it was spinning. We tried first pressing the start/pause button. The lid remained locked. Next we pressed the power button and the lid still remained locked. We tried starting a new wash cycle. The 'lid locked' light remained on. The only way we could open the lid was to use force. We took the machine to the repairer again. He put in a new locking device. When we got it home, again we managed 2 washes without a problem. On the 3rd wash the machine didn't like the spin cycle. It goes to the red spin light but the machine does not actually spin. The machine does not beep at this stage and will sit in that position until we turn the power off. When restarting the program, I have tried reducing the load. This seems to work. But I am curious as to why the machine does not seem to take the loads that it used to - even half a load. When my husband reinstalled the machine on both occasions he made sure that it was balanced.