I contacted armslist support to ask what was going on. They replied in just a few hours. This is the reply I received:
We appreciate your email. We're sure you've likely witnessed the site being down and unresponsive at peak hours recently. There is an issue with the filter logic, and our team is actively working on it to bring that feature back as soon as possible. For now, we have removed the filters so that the site is still operational. Our apologies for any inconvenience this may have caused. We appreciate your patience, and thank you for using Armslist!
We appreciate your email. We're sure you've likely witnessed the site being down and unresponsive at peak hours recently. There is an issue with the filter logic, and our team is actively working on it to bring that feature back as soon as possible. For now, we have removed the filters so that the site is still operational. Our apologies for any inconvenience this may have caused. We appreciate your patience, and thank you for using Armslist!