On a recent 3 week trip I used a handlebar bag (together with two back bags) to carry the stuff I needed. In the handlebar bag I carried a reflex camera, my phone, a power bank and some candy.
While my bike normally feels really stable, the first few days with the handlebar bag were a nightmare: the handlebar constantly felt really wobbly, to the point I had to check it was not loose. Then I got used to the feeling, but still could not completely trust the bike.
Can the handlebar bag cause such behaviour, and how can I mitigate it?
Edit: I had a picture of the handlebar bag to give an idea of the dimension. About the mounting, the bag itself is firmly held on the handlebar, and also the content did not have much clearance to move inside, maybe less than a centimeter. The reflex bag basically left only the space for the smartphone.