Please help!

I've been using old versions of Soundforge for many years (up to Soundforge 11) to record DJ mixes and convert cassette mixtapes to mp3. Absolutely love the product and it's always done everything I wanted and more.

I recently purchased Soundforge Pro 18, which has all the same features as the old versions, but there's an issue I keep coming across where Soundforge seems to apply some kind of automatic sound adjustment to my audio without me wanting it. It seems to happen mainly when I try to apply simple volume adjustments to one or both channels, but it also happens during other processes too.

For example, I have a stereo mp3 file recorded from an old cassette. It's about 45 minutes long. The file of the raw recording in Soundforge sounds exactly like it did on the tape, which is good. However, when I select a section of the tape (or the whole tape) and try to increase the volume of that section using the "process > volume" option, it changes the volume as I want but it also seems to apply some kind of auto correction across the entire 45 minute file at the same time. The file then sounds slightly echo-y in places, and the left/right balance seems to change on and off through the track, which is totally different to the original sound from the recording. It seems like it might be some kind of digital auto-enhancement, but I've trawled through all the settings and can't find anything that seems to be set to automatically adjust anything. Has anyone else come across this, and how can I sort it so it stops happening?

Not sure if it's important but I'm running Windows 11 on an ASUS M3500QA laptop.