@WTECH SAS I believe you are referring to saving a text or SSML format file of the audio content creation screen after you have setup the required text, voice and settings for speech output.
I tried the scenario, and it did not error out while saving the file with a different name, as saving the file name that already exists with save as option is not supported, you will see this message.
I think in your case, you did not see this message and the above error is seen instead.
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