Shading is problematic for all string inverters but based on various forum posts it looks like Delta has particularly poor/limited MPPT that can't handle even moderate shading.
That doesn't make sense from a functional perspective. I don't 100% understand how the MPPT 'sweeps the band' but I can see the results and I know what it's looking for. Current through a series string needs to remain the same and the current a solar cell passes is proportional to the sunlight it receives. So a shaded cell may only pass 1A while its neighbors in full sun are pushing 8A. The MPPT will 'see' that at (1A)(350v) it gets 350w OR (8A)(270v) it gets 2160w. It's gonna go with option 2.
The only area this gets complicated is with parallel strings. But Deltas have 3 or 4 MPPT trackers so having independent strings is possible. If they're paralleling strings then that's a problem with the installation not the inverter.