When trying to use /fill... replace, the command fails to run as the block state is unexpected, returning a syntax error. However, the command still fails to run without a block state and returns another syntax error.

/fill [coords] [coords] [block] [state] [mode] [block]

/fill ~~~ ~5~5~5 stone 0 replace air

Returns syntax error due to unexpected "0" (also happens with any other number)

/fill ~~~ ~5~5~5 stone replace air

Returns syntax error due to lack of block state

This makes the replace/outline/hollow etc features of the /fill command unusable, and also prevents /fill being used for anything but the default block permutations, e.g.:

/fill ~~~ ~5~5~5 planks 1

Returns syntax error due to unexpected "1"

The same issue also affects the /setblock command