User blog comment:B214/Question and Answers 6/@comment-86.153.130.40-20160802001312/@comment-9595671-20160802040507

My guess it's because due to sacrificing his left arm to Ddraig and then later being remade from the combined efforts of Great Red and Ophis.

He must have trouble with his devil wings simply because while a Devil, he's got more traits related to that of a Dragon, kinda like how Tannin uses his dragon wings alone despite four wings could do more.

When I see devil wings compared to other species' wings in the series, they seem thinner and more flexible. Compare those to a Dragons' wings which likely have more bulk in comparison.

Issei tends to fly using his dragon wings in balance breaker state, so he's likely more use to them, so if he tries flying with his Devil wings he might get a feeling similar to Phantom limb syndrome and doesn't fly correctly with them as a result.