Reserve match clashes with Champions League game issue?

[Sussex Hammer]

Bit confused here and hoping someone may be able to help?  In my second season and had a Champions League Group Fixture on a Wednesday.  Had as I always do placed some fringe players as "available for Reserves until match fit" to keep them ticking over and the No2 goalkeeper listed as always as "available for Reserves".  Come to Wednesday night and all players down as available for reserves have an orange box next to their names saying "playing in another fixture" which turns out to be a Reserve match so I am unable to select them for CL duty!!  Now I've never seen this before and in all incarnations of FM I  have assumed that First Team Fixtures take priority, hence why they were always available?  What's also confusing is that Reserve fixtures have been played on the same day as PL Fixtures but I haven't seen this clash before.  Is it a bug or is there somewhere an option to make sure First Team games take priority otherwise I'll have to untick all first team squad players from being available for the reserves.