@Mark IVE FOUND THE ISSUE!!!
Whenever I cap my FPS to 30, the animations (such as the rotating beacon and windshield wipers) appear to run at what I believe is the correct speed. However, if I remove the FPS cap and let the simulator run at around 75 FPS or higher, those same animations become noticeably faster than they should be.
While I'm glad I've found a workaround, I'm also a little disappointed that the only current solution is limiting my frame rate, as I'd much rather be able to take advantage of the higher FPS my system is capable of.
From the testing I've done, it appears that the animation speed may be tied to the render frame rate rather than the elapsed simulation time. In other words, as the frame rate increases, the animations also speed up because they seem to be updating based on the number of rendered frames instead of the amount of simulation time that has passed. Based on the sounds the wipers make corresponding to its movement, i believe somewhere around 40FPS seems to be the correct animation speed.
I've also noticed that this doesn't just affect the beacon and wipers. For example, when switching on the System 1 and System 2 electric hydraulic pumps, the hydraulic pressure appears to build much more quickly than expected, which makes me wonder if the same timing issue is affecting other custom systems as well.
I appreciate all the work that has gone into the F28 as it's one of my favourite aircraft in MSFS and I hope this information helps identify the cause. If this is indeed a timing issue, I'd really appreciate seeing a hotfix for it asap, as it has quite a noticeable impact on immersion, particularly for those of us running the simulator at higher frame rates.
Looking forward to hearing from you.
Kind regards, Leon