You can, but it probably changes the meaning a bit. Inconsistent could mean several things. It could mean inconsistent time-wise, it could mean inconsistent quality-wise, and it could be literally inconsistent, in that they use different practises in different areas.
Sporadic just means inconsistent time-wise, or possibly that there are gaps in the the records.
Note also that it should be practises...are, rather than practises...is.