I'm honestly not sure whether this will be helpful to you at all but ... My standard process, having edited the original .wav file (in my most common case, a church service) is to save the .wav file and then immediately do Save as.. (Ctrl+Shift+S) to .mp3. Clearly, this is to the same folder as the original and edited .wavs, but it has never (so far!) failed. The Save location is to an internal drive but I honestly do not know whether that has any bearing on this problem. So, the only difference between your solution and what I do is, because I do the save to .mp3 immediately after the save to .wav there is no neccessity for me to reopen the .wav because it is still open, thus saving one step in your workflow. HTH
... View more