Check valve is cheapest and easiest to replace.

Good to hear I'm not alone. We are having our fair share of really cold weather here ( no garage) and I haven't had a chance to do a thorough brake bleed. I'll let you know I make out. If you come across a fix please let me know.

Also check the rubber brake hoses going to the calipers. Look for bulging or other damage. If no visible damage, bleeding would be the next step IMO.

Will do. Thanks!