I've had both problems .. With the cover switches I found them useless so I bypassed them, so my cover has no effect now .. The roller switches most times can be cleaned with compressed air.. When cleaning doesn't work I compressed the roller by hand and make sure it moving up n down and also watch what the contact part of the switch is doing. If it appears that the contact is stuck I use needle nose pliers n gently bend them back into shape checking them regularly until I see that there working properly ... Both are very easy fixes ..
Mans Quest for knowledge,,, means he'll always find a way !!