A319 have this problems all the time, and I have seen some A320's also with this issue.
Following unofficial procedures seem to resolve this issue 90% of the time.
1. Reset the ATHR on the FCU, simple OFF / ON
2. Increase the Vapp 2 - 3 kts if seen creeping down towards Vls
3. If neither work, pull selected speed, consider going for managed Speed during final few hundred feet of the approach.
4. If all these above fails, go manual thrust, normally the ATHR reset on the FCU works