I worked with another gentleman that had a Samsung terrestial only receiver who had the same problem. Seems that when the Samsung loses reception of a station it's hard to convince it to look at it again. His receiver was new enough he could exchange it at Best Buy. My guess is there is a lithium battery or a nonvolatile memory chip inside that saves the settings even when the power is pulled. If it is a battery theoretically it could be pulled to reset the box to factory, BUT I don't know this for sure, and would recommend talking to Samsung especially if the box is under warranty.
You're probably right on target about the metal roof, 8VSB doesn't handle reflections very well in my experience. If you can get 3-1 which is currently at a lower power and a higher frequency then us and their tower is literally across the field from us, you should at least get 24-1. So either you have a bad reflection at our frequency or your receiver is playing games with you.
So if a rescan and power plug disconnection doesn't get you working again, you might try working with your antenna. If you could get the antenna even a few more feet above or away from the metal roof it might help. The towers are all NW of Wichita for the most part with UPN being slightly farther North.
UPNKansas is 1MegaWatt as in 1,000,000 Watts ERP (Effective Radiated Power) due to a high gain antenna. As far as a transmitter in the Salina area, nothing is planned. We are trying to get UPNKansas on as many cable systems as possible though (not digital sorry). We just bought a brand new transmitter for going digital in Wichita, so that kind of tied up our budget. We would love to be transmitting up there, but we trust that decision to the 'bean counters', and several things factor in to the decision.
In addition our DMA (Direct Marketing Area) makes a line N to S in between Manhattan and Emporia. This is why Topeka and other eastern cities would get KC and Topeka stations vs Wichita stations. Also why Manhattan sometimes gets both KC and Wichita stations. We would not be able to put a transmitter in for the Topeka market because of our DMA, but someone else might.
Our KSAS tower is not exactly omnidirectional but close. It has a peanut shaped pattern that is focused on Wichita and Hutchinson so areas SW and NE of Wichita lose our signal faster then people SE and NW.
Our crossover point between our Salina and Wichita transmitters for FoxKansas on I-135 is McPherson.
If you have a good outdoor antenna pointed West you should be able to get analog 18 KAAS on a good day. Our KAAS-DT is only 1kW so it's just making it to Salina. Unless everything was just right, I would doubt that you could receive 18-1 in Manhattan because of those hill like things you have up that way (what do you call that? terrain?)
Hope this answers some questions