At some point in the development of 1.14, chunk loading was limited to around players (and spawn). This causes many issues on the border of the loaded chunks. One of the worst examples I've tested so far is redstone:
photo_2019-04-10_22-25-54.jpg
But there are surely many other mechanics that break at the end of loaded chunks. I don't currently have a list of them.

Which mechanics should load chunks, which shouldn't and which can work without fully loading the chunk is a matter of discussion. Examples:

• a mob pathfinding into a new chunk
• an entity moving into a new chunk
• structure blocks loading in structures
• pistons pushing blocks into new chunks
• executing commands at faraway locations
• big explosions (they already work fine across the border of loaded chunks, without actually really loading the faraway chunks)
• hoppers transferring items into a new chunk
• …

New report for changed behaviour: MC-151049 (That doesn't mean that this one is fixed.)

Here is a video demonstrating the issue (or MC-151049, it's a bit hard to distinguish what the actual root cause is): https://drive.google.com/file/d/1HU4DsxURtYeS81oj1ecxYRhfoHBN-lq9