I have seen the reload of an app / channel you are referring to and that is not what is happening...
While it does vary by Roku model and which apps/channels are accessed, typically even for those with large channel counts, it will retain the last 10 or so channels accessed.
Meaning, even if I have 120 channels, if I only use 6 channels, Tablo being one of them, it typically wont re-download any of those 6.
They load without re-downloading.
However, occasionally I might venture out of my normal top apps, and yes it would re-download those I had not accessed in a while. With our slow internet speeds, this became VERY annoying so I added Miro SD cards to all of our Rokus and have not seen this behavior in years.
Again, I said all of that to try to better explain that scenario, this is NOT what is occurring here though.
The Tablo channel is working fine on mine but my parents are seeing the above issue (with far fewer Roku channels installed + MicroSD card same as ours).
The issue is that the big blue Tablo screen appears but the time it takes to find, access and bring up the first Tablo access screen, has tripled.
And it occurs every time they go back into Tablo after access Netflix or Hulu.