I am trying to analyze a phenomenon on our Matomo installation. When accessing our website, several users can constantly reproduce BAD REQUEST responses from Matomo while scrolling our page. For other users, this does not happen. My admins say there is no messages in Matomo logs about any errors.
Here is a screenshot how it looks like in Dev Tools Network Monitor:
Here are the Request headers of the failing request:
And here the Response Headers:
When looking at the Payload of the XHR request, it contains this:
hsr_vid=RE5OAX&hsr_ev[0][ti]=20872&hsr_ev[0][ty]=6&hsr_ev[0][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.997755%200.06697%20-0.06697%200.997755%2028.592806%20-22.534315)%22%7D%7D%5D%7D&hsr_ev[1][ti]=20888&hsr_ev[1][ty]=6&hsr_ev[1][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.999366%200.035597%20-0.035597%200.999366%2015.002031%20-12.210111)%22%7D%7D%5D%7D&hsr_ev[2][ti]=20838&hsr_ev[2][ty]=3&hsr_ev[2]=0&hsr_ev[2][y]=406&hsr_ev[3][ti]=20905&hsr_ev[3][ty]=6&hsr_ev[3][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.999998%20-0.002094%200.002094%200.999998%20-0.868824%200.734786)%22%7D%7D%5D%7D&hsr_ev[4][ti]=20922&hsr_ev[4][ty]=6&hsr_ev[4][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.999289%20-0.03769%200.03769%200.999289%20-15.399994%2013.501651)%22%7D%7D%5D%7D&hsr_ev[5][ti]=20939&hsr_ev[5][ty]=6&hsr_ev[5][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.997466%20-0.071149%200.071149%200.997466%20-28.653149%2025.982954)%22%7D%7D%5D%7D&hsr_ev[6][ti]=20956&hsr_ev[6][ty]=6&hsr_ev[6][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.994301%20-0.106611%200.106611%200.994301%20-42.267946%2039.722861)%22%7D%7D%5D%7D&hsr_ev[7][ti]=20972&hsr_ev[7][ty]=6&hsr_ev[7][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.989876%20-0.141938%200.141938%200.989876%20-55.385013%2053.938709)%22%7D%7D%5D%7D&hsr_ev[8][ti]=20994&hsr_ev[8][ty]=6&hsr_ev[8][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.984564%20-0.175023%200.175023%200.984564%20-67.260914%2067.736969)%22%7D%7D%5D%7D&hsr_ev[9][ti]=21006&hsr_ev[9][ty]=6&hsr_ev[9][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.97771%20-0.20996%200.20996%200.97771%20-79.364917%2082.824742)%22%7D%7D%5D%7D&hsr_ev[10][ti]=21022&hsr_ev[10][ty]=6&hsr_ev[10][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.969616%20-0.244631%200.244631%200.969616%20-90.924166%2098.333821)%22%7D%7D%5D%7D&hsr_ev[11][ti]=21039&hsr_ev[11][ty]=6&hsr_ev[11][te]=%7B%22att%22%3A%5B%7B%22id%22%3A969%2C%22attributes%22%3A%7B%22transform%22%3A%22matrix(0.960876%20-0.276979%200.276979%200.960876%20-101.292698%20113.297863)%22%7D%7D%5D%7D&hsr_ev[12][ti]=21055&hsr_ev[12][ty]=6&hsr_ev[12][te]=%7B%22att%22%3A%5B%7B%22id%22%3A882%2C%22attributes%22%3A%7B%22class%22%3A%22frame%20frame-type-text%20frame-layout-0%20frame-space-before-none%20frame-space-after-medium%20frame-padding-top-none%20frame-padding-bottom-none%20frame-%20ce-icon-inframe%20ce-icon-block-left%20d-flex%20d-sm-flex%20d-md-flex%20d-lg-flex%20d-xl-flex%20d-xxl-flex%20aos-init%22%7D%7D%5D%7D&hsr_ev[13][ti]=21056&hsr_ev[13][ty]=6&hsr_ev[13][te]=%7B
We are using the following plugins:
A/B Testing
Heatmap & Session Recording
Conversion Export
There seem to be no direct consequences of these errors, tracking seems to work fine, but we are determined to find and eliminate the cause. We’re just out of ideas how to track this down further.
Can anyone help with finding the origin of this failing message (what is this Payload about?) and help to narrow down the cause for the BAD REQUEST?