Hi! The described behaviour depends on -Dpd4ml.cache.images.in.tmp.dir=true JVM setting and not-graceful shutdowns of the application, as the .dat files are created with tempFile.deleteOnExit(); property.

We’d recommend to update to PD4ML v4.0.16 (available as a snapshot build; it is going to be released in few days) with better cache control and change the JVM property to -Dpd4ml.cache.images.in.tmp.dir=false