Error: WebGL: texImage2D: Conversion requires pixel reformat

In game preview mode, I’m often getting this error in my project, as reported by Firefox:

      "Pixi.js 3.0.8 - WebGL - []("  pixi.js:7:2660

Error: WebGL: texImage2D: Conversion requires pixel reformatting. pixi.js:4:28852"

The game works with this error, but it repeats a lot of times.

From time to time, I also get a strange timer issue that causes rapid bullet fire (timer doesn’t work or something like that) in certain browsers (IE constantly, Firefox sometimes only). This is an additional note, but may or may not be related at all to the WebGL error. I’m using a standard timer event for bullet fire, but it is enclosed in a “for each object, repeat” which makes sure that each turret placed on the scene will fire a bullet. When exported completely, however, using Cocos2D and then HTTP local server, the game works fine in IE also, no timer/bullet issues.

The bullet issue might be my fault too, but as it works fine most of the time, it’s a bit suspicious. Here’s the event sequence used to fire:

The first part is related to isometric display (360 images for 360 angles and some conversion to adjust frame number with angle).