DAR changes a lot for DVB SD channels. Old TV programming is still 4:3. So some channels often switch between anamorphic 16:9 and 4:3 mid-stream. Kodi does not seem to recognize that, resulting in a stretched image after the switch.
I used latest Krypton nightly from today, as I have seen some recent commits by @Koying concerning AMC and DAR.
I am attaching a sample which demonstrates the incident.