I just noticed a couple of files I converted from FLAC to M4A (AAC) with Selene Media Encoder + Nero AAC now have substantial clipping and distortion in them even though the original FLAC had none and in fact didn't have a single sample touching 0 dBFS anywhere.
Is it normal for the pure and simple conversion to a lossy format to produce higher peaks (and in the case of normalized originals a real risk of clipping) or should I suspect problems with how the conversion is being performed by the particular software I'm using?