SRAM Guide brake lever won't return I have an SRAM Guide brake (rear) that after bleeding, the brake lever won't return quickly.  At room temperature, this is barely noticeable, but when the temperature climbs, or the bike is in the direct sun, it takes about 30 seconds for the brake lever to return fully.
This happens every time I bleed it and lasts for at least a couple of weeks.  The front brake, bled the same way, at the same time, has no issues.
At first, I was thinking that there was too much fluid in system and when it got hot, the little bit of expansion would lock up the piston.  However, when I popped the top bleed screw while hot, only a little bit of fluid came out and the lever was still sticky.
I am now wondering if the tolerances inside the lever are too tight.  Once the barrel warms up, it shrinks enough that the spring can't overcome the friction...
Any other ideas?  Should I just give up and try a warranty return with SRAM?
This is typically caused by seals which have become soft and sticky due to contaminates like degreaser.  It also happens over time, and SRAM Elixir brakes are especially known to have this issue. 

The Guide series hasn't been bad about this so far. 

The solution is to replace all the seals in the lever.  SRAM has a special grease (Avid DOT Grease) for this purpose, or you can use DOT 5.1 compatible grease.  Regular grease will damage the seals.