I’m sure I’m not the only that see some routes that you can’t achieve a platinum medal despite having all safety systems, riding under the speed limit everything. That happened to me on multiple routes
That’s absolutely normal, the achievement system with medals is broken on some services, even when running at 1 kph and all safety systems on, you can only obtain bronze.
Unfortunately the medal system has always been a broken which is one of my major gripes. I don't understand why they've had a feature to sign journeys off with "Completed to gold" when a lot of the scenarios and services cannot be completed to gold. SEHS is a frustrating one for it on the freight layers. And some scenarios allow you to reverse back and fourth to make the points up slowly but we shouldn't have too. One user did collate a whole database of services that were unable to be completed to gold with everyone reporting in but unfortunately that's another thing DTG did nothing with and the forum user gave up in the end unfortunately.
What DTG should really do is drop medals for services altogether, it's clear that it's too much of a workload for their bug testing teams to pull off. And what evidently little time they have for testing should solely be focus on making sure services are completable, nothing else. If medals/scoring has to be kept on some level do it for scenarios, much easier to test five scenarios than 50 to 1000 services, plus would help differentiate them a bit more from timetable to boot.