I am unsure about this issue. It seems like Railcraft is not properly reporting back its internal tanks.
I will see what I can do about it

I am sorry, but I had much more to do that I thought. I had a few free minutes today. So I fixed thiss issue, finally. Thanks for reporting! :)

Forgot to say: I will publish the new version asap. However, most likely not today, sadly

Sorry for the delay! Uploading the new version right now