Kapur had five bogeys against just two birdies and will need a special round on Sunday to get back to a good finish.
The 24-year-old Danny Willett moved into a one-shot lead going into the final round. Seeking his maiden win, he carded three-under 69 at Gut Larchenhof to move to 12-under.
Kapur bogeyed the second, eighth and ninth and birdied only the seventh on the front nine. A birdie on 13th was followed by bogeys on 14th and 18th for a disappointing 75.
Willett turned in 35, holed a huge putt across the green for a birdie at the short 11th and after another gain at the 14th, pitched to six feet at the par-five 16th for his sixth birdie of the day although there was a third bogey at the last.
Willett is one ahead of compatriot Chris Wood and halfway leader Joel Sjoholm, with South African Keith Horne and Australian Marcus Fraser