How much time does it tale to process a fax? Timer events will queue up while things like other code runs. If your fax processing takes longer than 5 seconds then that timer will keep queuing up until all the faxes are gone.

Also, something else to look at. Your larger timer interval is a multiple of your smaller one. One timer event is always going to be overshadowed by the other event. Try making the second one 31000 or the first 7000.