What were they created with? What was their bit depth and sampling rate?
I've noticed that wave files made at 8 bit or 22.05kHz with SFXR often times won't play in Construct, even if they play in other audio programs. Converters and sound editors might add funky header information that Construct doesn't like, as well. Or so I've heard. So it might not have been a Construct issue. Well, not totally anyway.
Suffice to say you should be able to autoplay .wavs no problem, especially if they're short.
Anyway, if you still have the originals you might be able to open them in something like Audacity and re-save them. That usually fixes any sounds that are broken for me.