Sometimes I get peak value 366.52 dB for 0 db files in “Normalize level” window. Re-detecting (Find current peak value) gives me 0 dB, another try gives 366.52 dB again 
What is going on? I believe it has something to do with the function “Convert to mono (Mix)” (Edit → Copy selection to new window) e.g. converting stereo file to mono and checking its peak gives me weird values.
I can also reproduce an anomaly with this peak display, for mono files. You can use the Audio Analysis tool, instead.
Good that you can reproduce. Yes I do double-check with Audio Analysis.