2-3 second Delay in loading images in master slide in HTML5

Hi, I'm new here! I have created a Storyline lesson in HTML5 for playback within another system on an iPad. When running the course on the iPad browser (not AMP), I see a pre-loader is displayed for upwards of 2 seconds between each page. This seems strange as all the content is local. I have also tried it locally on my PC through a standard browser and I encounter the same issue. Does anyone know if there there anything we can do to remove this pre-loader delay by either a Storyline re-compile, or a backend hack of the code? I am applying a full screen image to the master slide and I can solve the problem by deleting this image from the master slide, and applying it to individual pages. The size of the image itself is 23.8Kb. Applied to each slide there is no real delay, applied to the master slide, the delay is 2-3 seconds between images. I repeated this by adding a 2Kb image to a master slide of another course, when published and ran it in HTML 5, the course shows a 2-3 second delay between slides. Incidentally, there are no such delay when using story.html. This is an issue only when we use story_html5.html to run.