Problem with rear hatch struts

[Hope26]

Hi everyone,
I am new to this forum and am glad you are here. I have a 2005 Sienna Braun RampVan, a handicapped conversion van. Last week I had a problem with the rear hatch closing. I pushed the electronic button to close the van up after getting my wheelchair in and the rear door started coming down and then reversed itself to go back up and then came back down and was not closing. I could not do anything to assist so I called out for help from someone in the Walmart parking lot. The next day I took it to the conversion place and they replaced the struts. It kept doing this so they told me to take it to Toyota. When I went there it didn't do it but what I realized was that it was not sitting in the heat but in their garage. I observed that the heat from the high temperatures here in Florida was causing this. Has anyone else had this problem? Toyota told me to take it back to the conversion place and I am going in circles...

Thanks for any suggestions or help,
Hope26