Mix Stereo to Mono Speeds up Bug!

I think There’s a Bug in Audacity when you Mix Stereo Track to Mono by using “Mix Stero Down to Mono” There are some sped up effect for the Mono Mix.
Some people say it is because Sample Rate become changed that’s why. But I think its doesnt supposed to happen. Cant do a simple Convert Stereo Track to Mono because of this bug. Please fix this. Thanks.

I cannot reproduce this on W10 with 3.0.2 or the latest alpha test build I have for the upcoming 3.0.3

There is no speed up or pitch change - and the sample rate of the track remains unchanged.