Digital BW, The Print

Hello,

I'm using spongeless carts from MIS with UT-FS ink in my 1160, and
what happens now and then is that the black ink runs dry (it stops
printing black), even if I just refilled the cart. I can get it to
flow again by doing cleanings etc, but after a couple of prints it may
very well happen again. I'm spilling a lot of ink, paper and time this
way (not to mention my nerves).

Does anyone know what causes this and how I can prevent it? Is the
cart perhaps defect?

Thank you.

I g o r