Occasionally I was still hearing grinding going into fifth

I had to have the transmission replaced (manual 5) due to a leak in the transmission case. Then this past July I was having problems again and needed some gears replaced. At this time I had the clutch replaced. Occasionally I was still hearing grinding going into fifth. The shop replaced a bearing. Two days after picking it up I got stuck not being able to shift and when driving it would start moving even with the clutch off and lurching with the break on. They replaced the slave cylinder (originally replaced with the clutch although with two defective parts). I again picked up my truck and in less than 24 hours, the same thing happened. Now they say it is not the slave but the master cylinder. Does this sound right? Any ideas why I am having so much trouble? Time to get rid of the truck?