The bug
In previous versions, items thrown into lava would bounce out while getting caught on fire. This was intended (MC-54861) (and I liked it personally 😛). In 19w07a, this behavior stopped working. It worked in 19w06a and below. No changes regarding this were mentioned.
How to reproduce
1. Throw some items into lava
→ ❌ They fall right in like it's water instead of bouncing
I think this is Working As Intended based on Bedrock 1.16.20 parity. (See MCPE-65372 )