Zooper Tango Twin Stroller unfolds randomly when...

Question

Hi I have this stroller for my twin boys and having just used it twice the first time we had to bring it back to the shop for a replacement. The problem is when unfolded and ready for use when our babies are reclined and we are pushing them the front two bars behind each wheel open if we lift to go up kerbs. This in turn gives the impression that the stroller is going to fold back up with our babies inside. It's very annoying as we've tried everything and are getting frustratingly afraid to use it. We have to keep clipping them back in place every time. We are well aware of the locking mechanism but it just seems that it's not working as intended. As i said we have already exchanged it once because we thought it was broke but it's actually the same as the original one we purchased. Could someone please give me a fix if possible as I don't wanna buy another stroller I really like this one. If there is a certain weight required as instructed it would still be the same I think as it appears the more weight put on the back the more the stroller unlocks,Please help a very disgruntled dad