I'm experiencing this as well, also with loader images. I have four charts that use loaders in frames until the charts are displayed. The first couple of loaders are displayed correctly. The second two are cancelled (in both Edge and Chrome). This worked previously, so it seems some requirement has changed in the browsers. While turning off content expiration in IIS might work for a single user on a single PC, it isn't a solution for thousands of PCs across a company network. I came here looking for a solution, so I apologize for not having one to offer.