Is there something wrong with the data from the Bittrex Exchange for the Clam/BTC pair. Other currency pairs seem to be working.

Same here, but on all pairs.
Are you guys using the demo? If yes, does a restart fix it?

What you see you be caused by network problems, and could be temporary.
I'm using the demo version. I logged off last night and then logged in this morning and find there is only 1hour of data.
that is strange we will look into it. But I am not seeing the same behavior here. Is anyone else having this issue?
I am having the same issue (unable to see historic data), but only with certain pairs.
For some strange reason, every time I close and re-open leonArdo (or after it crashes), the BAT/BTC pair on Bittrex comes back with only has about 2.5 hours of data - all the rest is empty. It doesn't seem to be able to sync with your data-collection service, and it looses all data it had collected by running here after a restart.
Also on Bittrex, SC/BTC suddenly lost all past data on June 3rd, about 4-5am. It's as if the coin got created there. I cannot see anything of the past.
Is there any specific DB file for the coin I could try deleting in the .leonArdo folder for those?
Thanks for pointing this out. Actually, our data collection is running continuously but needs to be re-started to pick up new coins that are added to the exchange.
QRL, for example, was only added 9 days ago and that's why we were missing data.
I've re-started the data collection and it will gather data on those coins now.
We are also working on filling gaps for data we missed.
Best wishes,
Jonathan