It seems something is wrong with your texture. While we'll be fixing this problem you can export it to PNG format, it might help.

Let me know if there is anything else you want from me

Could you also send bump texture you're using? (other textures aren't necessary)

Good day. Thank you for taking an interest in Blend4Web.
Could you please attach to one of your posts the blend file with a scene that doesn't work, so we can see what's wrong with it?