AF POINT keeps losing my setting

When using the 17-40L lens with the 5D mark 2, I notice that the AF point that I have set to the central point keeps losing that setting and often any AF point will get used. I wondered if it was from changing modes frequently or some other thing that Im doing

I have tried cleaning the points on the lens but apart from that I cant think of anything that might change this

Am I inadvertently doing it myself? What things should I consider?

thanks

Is it only the 17-40 which causes this behaviour? Have you tried resetting the relevant custom functions back to default etc.?

I think its only the 17-40 but havent really tested other lenses much as its the 17-40 that I use 78.9527% of the time

I may have to rest the custom functions I suppose - what a palaver though to reset them

If you go from any creative mode to green box mode, it will revert to using all points.
If you select a point when using any custom mode, C1-C3, it will go back to whatever you had before when you return to Tv, Av etc.

apersson850 wrote in post #7898841
If you go from any creative mode to green box mode, it will revert to using all points.
If you select a point when using any custom mode, C1-C3, it will go back to whatever you had before when you return to Tv, Av etc.

I never use green box mode ( not intentionally)

It looks like either a camera or lens problem then?