What do you mean by erroneous?
The protocol requires that timestamps be greater than the median of the last 11 blocks and less then 2 hours into the future from your own perspective. If you get a block more than 2 hours in the future you won't accept it until its within 2 hours. Any timestamp that passes these criteria is valid, anything else will be ignored.
If yes, can these timestamps have a negative effect on the inflation schedule or locktimes?
Time based locktimes aren't based on the time on the current block anymore, but instead are based on the median of the last 11 blocks (the lowest timestamp the block could have).
The allowed 2 hour difference on the blocks timestamp allows a one time 2hr/2week = 0.5% difference in inflation, -- utterly irrelevant and well below the noise.
Once again I have learned something. Happy days, thank you.