Just finished a strip with solid behr latex on the rails. Like Ken said strip strip and more strip. Mine was fresh behr (2 weeks) so it may have been harder than yours, if its already failing. I wouldn't count on it though
We did two applications of high strength HD80 (
www.esproducts.net) and kept it wet for 20 minutes at least each time. When it comes off it gets on everything. Pieces of behr latex on clothes, pressure washer, house, yard, you name it. Luckily got the majority of it off, but then its time for several hours of sanding. Ended up replacing the top handrail simply because it wouldnt all come off