Pictures can help us identify what could have happened. We see this rather often, as the pressure in the buckets can be very powerful. Much like a bag of chips expanding when traveling at high elevations. It is good to keep in mind that we are located in Salt Lake City, Utah which has quite a high elevation. The pressure changes as it travels across the country and can cause the plastic to warp. However once you open the buckets the pressure will be released, and relax back into shape.
The airtight seal forms whenever you firmly affix the lid, so you can open and close it as many times as you would like without compromising seed shelf life, as long as you close the lid tightly when finished. Happy to work towards a solution as needed, please let us know your thoughts.
Thanks!