[10:01:25 ERROR]: Invalid entity-per-chunk-save-limit config, 'ender_signal' is not a valid entity type. Correct this in paper.yml.
[10:01:25 ERROR]: Invalid entity-per-chunk-save-limit config, 'firework' is not a valid entity type. Correct this in paper.yml.
[10:01:25 ERROR]: Invalid entity-per-chunk-save-limit config, 'splash_potion' is not a valid entity type. Correct this in paper.yml.
[10:01:25 ERROR]: Invalid entity-per-chunk-save-limit config, 'thrown_exp_bottle' is not a valid entity type. Correct this in paper.yml.
Corrected in 3e5f77b.
Apparently bukkit's EntityType enum does not reflect mojang entity IDs, so there's that.
Correct IDs can be found on minecraft wiki of all places.
Paper writes this error.