AST 1280XR Tach Signal Won’t Stay Programmed

Hi, I was wondering if anybody else is having problems with the AST 1280XR Remote starts tach lead. I have installed hundreds of AST 1250's and 1270 R/S units and have had little issue. The new 1280's however have been a pain. The tach rate (blue/white) won't stay programmed. I've set it like the manual says and also manually programmed it like the manual says and for some reason some (not all) of the units come back with vehicle not starting or keeping the starter engaged. AST says there is no problem. I have used the same soldered connection techniques for install using either an injector wire or other tach lead. Has anybody else seen this issue? AST tells me to let the unit learn at the lowest possible tach rate. Usually putting the vehicle into reverse and then learning it. I'll give that a shot from now on. I just hope these things are not going down hill in quality. I like these units for features and ease of installation. Jon Traveling Electronics