Hopefully someone has got further than I have in tracing this issue...

Banners, both skinobject and module instances, are periodically not rotating on our portals.

I've got ~50 sites running on DNN 4.3.5, and the banners simply stop rotating on all sites for up to 12 hours at a time, start rotating again for an hour or two, then stop again.  They sometimes, but not consistently, rotate again after an app-restart.

All of the info I could find pointed to a schedule or caching issue, but I've systematically disabled every item on the schedule, the sheduler itself, and caching and had only a slight reduction in this issue - which may be wishful thinking.

The only modification I've made to the banners procedure is commenting out the last line to fix child portal banner links.

Any ideas would be appreciated.

Are you using a caching/compression tool such as PageBlaster? I ran into the same issue and it was indeed PageBlaster. The workaround was to exempt those tabs the app.

If you look at gemini you will see there are about 14 outstanding issues to do with banners at the moment in the private project. That appears to be one of them unfortunately... cheers..