Is losing fix near one building really worth ripping out a whole working setup over? That metal shed is just multipath, any base or rover near it is gonna bounce signals off that thing, so blaming the radio part does not add up. The fact that the other crew's 900 MHz base worked a hundred feet away tells you your radio is probably fine and something else got moved or set wrong. Going NTRIP for $1,800 just trades one problem for another, because now you are betting on cell bars out in the middle of a field, and when that tower gets weak you lose fix across the whole site, not just by the shed. Honestly staking hubs is a pain but it never drops a fix when the sky goes gray or a tower hiccups. Fix the multipath first, move your base, check your antenna, and see if the problem even follows before you spend money on a new system.