CLASSICAL MUSICIANS AND CLICK TRACKS
Don’t expect every musician to be able to record with click tracks. Classical musicians who don’t do a lot of film work often have big problems when recording with a click track which has several reasons:
First of all, classical orchestras usually don’t play on the beat (that they get from the conductor) but slightly behind it and it is very tricky for them to just simply do it differently and play on the beat. Secondly, covering their ears with headphones that gives them a click (even if it’s just a one sided headphone) impairs their ability to hear themselves and other musicians which however for them is a massive part of controlling their playing and sound.
So before you record with musicians, ask whether they are okay with click tracks. If you see a problem coming up, a solution would be to get a really good conductor and only give him/her click track. However the result might not be tight enough for certain hit points in movies as every musician only looks once in a while at the conductor (the other time being busy reading the score they’re playing of course).