With respect, while the preamble in the CC might not be consistent with events, it is just that, a preamble. It is a red herring in terms of process - the only matters which a CC must contain are:
Charge certificates
5(1)Where a penalty charge notice is served on any person and the penalty charge to which it relates is not paid before the end of the relevant period, the enforcing authority may serve on that person a statement (in this paragraph referred to as a “charge certificate”) to the effect that the penalty charge in question is increased by 50 per cent.
And it does.
Furthermore, it correctly advises what might happen next even though there is no regulatory or legislative requirement to do so.
If their struggle with dates and periods is systemic there might be a procedural silver bullet 'going forward' but only when the PCN is received and this won't happen until the procedure mentioned previously is followed.
OP, I suggest you just wait pl.