hi there Mojang this is a very old bug that I found in bedrock ,ok so when you change the random tick speed to be very high like 1000or2000 in the world setting before or after world creation at first nothing really happens the player movements is normal, but when you place or break blocks the breaking animation and item drop (affects all items) is verrrrrrrrrrrry slow but the player fps is unchanged therefore it's not lag  plus mob behaviors are also the same story their hit animation, their slight jump, death animation, and mob sounds etc.

This bug also affects  the player's ability's to make grass paths, plant/mine crops, mining (all of these are slowed down significantly),also this affects throw snowballs firecharges ender pearls, eyes of ender,  bows, crossbows, fireworks (they all slow down or stay in place then teleport to their designated location)