GPT-5.1 broke my custom GPT actions

@OpenAI_Support

We are also experiencing frequent issues. This lack of stability is a very serious problem.

I would like you to investigate this urgently. Also, if there are any alternative solutions or workarounds, please let us know.

Is the quality and stability better when using the ChatGPT apps?

We are reaching the limit of what we can tolerate, so I would appreciate it if you could share the best approach or recommended methodology.