Thanks for your testing.
There have been numerous changes in 1.10 to the shader generator in an attempt to make the texture blending behaviour better match the fixed-function pipeline. It could be that there is a bug, or that your application relies on the incorrect behaviour from 1.9. Did your application work correctly in the fixed-function pipeline in 1.9?
I’m happy to help you get to the bottom of the issues; I can help you debug if you privately gave me access to your application. Otherwise, it would be helpful to get test cases if you narrow down the individual issues. (If you are having trouble figuring it out, it’s also an option to generate an apitrace file so that I can step through the OpenGL calls and find out where it’s wrong, but it’s more helpful to first isolate the problematic areas.)
As for alpha blending, the only thing I can think of at the moment is that the default alpha blending operator has subtly changed in 1.10; you can try setting “old-alpha-blend true” in Config.prc to enable the old behaviour and eliminate this as a potential factor.
What do you mean when you refer to the performance? Have you seen a performance increase or decrease after upgrading to 1.10?