Sorry, no solution here. I have two 740s (actually one 740 and one 740i). The 740 has experienced the same problem as you describe, but it also gets fairly heavy use at my business. The 740i is for home and gets low usage. I don't work at the office where the 740 is located, but I did see the problem occur and there wasn't anything obviously mechanical wrong with it. The lady who uses it, though, said the problem hasn't been happening lately. Probably a dirty sensor/switch, though I wouldn't rule out lube. Please let me know as I expect to move the 740i to one of our business locations where it may develop these symptoms.
mjk