Complex sentence: One Ju 86 had already been converted to use radial engines as a testbed for possible export versions, and this showed much improved reliability, and production was switched to a version powered by the BMW 132 engine, the Ju 86E, production continuing until 1938.
Split into simpler sentences: One Ju 86 had already been converted to use radial engines as a testbed for possible export versions, and this showed much improved reliability. With production switched to a version powered by the BMW 132 engine, the Ju 86E; production continuing until 1938.