if it's not everytime you use the sat that you get redness and pain then it probably isn't an allergy or something, just thought i should suggest it incase it may seem a possibility to you.
It may not be nessecarily you thats doing something wrong, your body is full of veins capillaries etc, so i think its perfectly normal to hit a blood vessel now and then which causes a little bleed. especially as it's worn 24/7 and as your moving around so will the cannula.
The ones that go in at an angle i haven't tried yet, i'm far too happy with my current steel ones to venture to those yet, but i presume it must take precision and skill to get the hang of it though!
If you get recurring pain, redness, or anything you think is out of the ordinary don't ignore it. a simple set change could help or switching to different sets, in the past Donnellys dogs has has a faulty batch so don't always assume it's your technique and explore others reasons too if you seem to experience the same problem frequently.
The other week i changed my set in the morning, my BG's were fine all morning, no rise or anything strange. Then all of a sudden in the afternoon it's was awfully painful, i couldn't touch it at all, and i daren't change it until i got home because i felt i might be in tears it hurt that much to put pressure on it... when i got home and changed it, i really was nearly in tears and it took me about 15 mins of tiny pulls to get the horrid thing out. It was quite bloody and badly bruised too
. I have no idea what caused it as i always put a little pressure on it when i've put a new one on to sort of test it and wiggle around a little to make sure it's fine. It just seemed to become painful out of the blue!