Chances are, it's the lens you're using. This is a common issue with
some photo lenses and your second photo is a good example of what you would see. I would try an alternate lens and see if the issue still persists. Kolarivision, who does camera IR conversions, has a list of troublesome and non-troublesome lenses on its website:
Lens Hotspot Database - Kolari Vision
You might find your lens listed there but in any case, I doubt that it's the infrared filter's fault. I've used Zomei filters with no problems, and think you're changing the main lens will solve the issue.