Spawning high above World Spawn and fall to death on server join

After upgrading Bedrock server from 1.7.0.13 to 1.8.0.24, on two occation I've experienced suddently spawning high above ground at World Spawn coordinates, even though I logged out and shut down server gracefully the night before. When it happened I had all my stuff, but then of course fell to my death and had to go retrieve (luckily my settlement is close to World Spawn),

This bug never happened on 1.6.1.0 or 1.7.0.13. The world I'm playing was generated on 1.6.1.0, then upgraded to 1.7.0.13 and now 1.8.0.24.

Bug isn't consistent, happened in two of mayby ten logins withing the past days.