Amazon Polly switches and mixes Standard voices with Neural voices randomly.

When using Amazon Polly with Neural voices, Amazon Polly will switch to the standard voice.

To repro try pasting this text into the Amazon Polly Console. Use Joanna or Matthew (neural, no SSML) Observe how the 1st and 3rd sentences are read using the Neural voice, while the second sentence is read using the Standard voice. This is affecting a lot of our customers and would appreciate it if it is fixed.

This is my first sentence and it is read out using the chosen Neural Voice.

This is the second sentence and will switch to standard (f), through (h), a prospective primary E D E Entity and prospective phase change E D E Entity must retain one or more independent third-party contractors. This is the third sentence and now it is back to using the Neural Voice.