Problem cutting traced bitmap

[plotski 0]

Got back into vinyl signage after a 12 year "retirement." Just today set up my MH 721 and, despite having to cut at the ridiculously low downforce of 10 grams on premium (cast) vinyl, have had only one problem.  When cutting a traced bitmap from CorelDRAW 7.0 (using CorelTRACE), I noodled the vector nodes to my satisfaction and exported from Corel as an AI (Adobe Illustrator) file.  I opened it in SignCut-X2 PE and can cut it fine at 8".  However, when I size it to the 22" inch width that it needs to be for a sign, the plotter stops at midpoint (while the SignCut software continues to spool).  Is this a problem with the plotter's buffer?  The file isn't terribly complex, but it does have slightly over 1000 nodes.

Also, why does any downforce setting over 10 grams cause the plotter to cut through the vinyl paper backing?  I do have the blade retracted so that it is less than the thickness of the vinyl.