Those look like no data pixels, I just wrote a post about using the Reclassify value tool to fix no data.
Fix first no data before any thing.
Test and if spikes remain then try convert data type.
Start with a new untouched source file
Start with a small section that fits within a Level 12 grid as shown by the Aero Scenery Tool to avoids mask which this probably isnt, but to be sure its best for now till we narrow down the problem.
Fix no data before converting data types.
This is what I suggest you try.