Normally if there are fatal errors on the ticket, the clerk at the ticket office will cancel them. When the building owner went through MLEO training, they were instructed to initial corrections.
If it does go to trial, keep in mind that the Provincial Offences Act allows the courts to amend the ticket.
http://www.e-laws.gov.on.ca/html/statut ... ]Amendment of information or certificate
34. (1) The court may, at any stage of the proceeding, amend the information or certificate as may be necessary if it appears that the information or certificate,
(a) fails to state or states defectively anything that is requisite to charge the offence;
(b) does not negative an exception that should be negatived; or
(c) is in any way defective in substance or in form.[/quote]In my honest opinion, I don't believe what you described is a fatal error.
Economically speaking, it's in your best interest to pay both tickets. Depending on the city, they may offer up to 50% off the set fine.