I am seeing a similar issue. With mine, the skeleton horses are rapidly losing health, resulting in their death despite no movement, suffocation, etc. This is on Bedrock on Windows 10 in a local world.
I reported one of the bugs duped to this one; people asked me whether I was playing in Realms (no, simple world) and what platform - both I and the host were playing on Windows 10.
I am seeing a similar issue. With mine, the skeleton horses are rapidly losing health, resulting in their death despite no movement, suffocation, etc. This is on Bedrock on Windows 10 in a local world.