Welcome to Android Central forums. Sorry to hear you're having issues with your phone. We talk about unlocking phones like with your issue but we don't talk about forcing a lock or by-passing security in any way. Do you think your situation here would require some brute force way of getting past the pattern security installed on the device?
In the meantime, there is a setting for how the pattern appears. It can be one long continuous line between each of the dots or it can be a momentary line that disappears as you reach each dot. The latter would look as if the line was cutting off before the pattern was complete but regardless the pattern should complete and work if it is correct. Having said that things that could have an effect like you're describing would be things like, if the screen was wet. If the screen was wet in some way it might see two touches when there is only one. A loose or dirty screen protector may have the same effect of making the screen think it is being touched at two points at the same time or cause dead spots if it becomes loose or partially raised on a corner. I've also heard that really dry hands have trouble with some touch screens. I don't believe I've experienced that one but I've seen mention of it happening.
Clean your screen, consider removing your screen protector or remove it if it's in bad condition, try some lotion. Let us know what you find and we will offer you some more advice.
What device do you have? If you have a Samsung there might be an online way to unlock it using Find My Mobile trough your Samsung account.