First level of enchantment table is empty

My level 28 character went to use enchantment table on fishing rod. First level (4) had no enchantment listed, second level and third level had enchantments. Have all bookcases.

First time I have seen enchantment table without enchantment available, so assume it is a bug.

There is an enchantment in first level (6) with normal operation, but bug occurs when using block of dirt to block 2 levels of enchantment so top level only requires 28 levels instead of 30.