This started happening for us when merging the following changes from 5.5 into our version of 5.4.4 (35220151 and 34716409) as described here https://udn.unrealengine.com/s/question/0D5QP00000QF0vc0AD/editor-crash-when-ddc-request-for-texture-streaming-in-failed
It fixed our crash, but we had to rollback as we started to experience this exact issue.