Minecraft 1.13-pre4, Minecraft 1.13-pre9
The condition "random_chance" is supposed to take a value from 0.0-1.0, however it's requiring a lower decimal to perform as expected when there are multiple entries.
When specifying the condition:
the loot from the entry is dropped nearly every single time. However this change to the "chance" decimal:
works out to a 10% chance to drop. The more items you have as entries, the lower you need to have the chance decimal to work correctly.
Loot table where this happens attached. One with a few items that drop more often than 10% of the time, the other table with items where they are dropping constantly.