J F Ogilvie
You have a very peculiar way of expressing your points of view ... I will disregard that for this one time and try to help you with the contents.
The Maplesoft Physics Updates work fine with TTY cmaple, and also with the Standard Interface distributed with Maple, maintained by Maplesoft, and also with the not-maintained-anymore-since-years, so-called "Classic," ancient interface, the one you say you want to use, that was developed in the 1990s, provided that Maple itself runs properly in that interface.
IMPORTANT: the Maplesoft Physics Updates require you to have installed the latest Maple version (2018.2.1). If that is not the case Maple will warn you and point to the webpage from where you can download a version of the Updates for your version of Maple.
Now, that there are other things in that ancient "Classic" interface not working the way you expect, as you are saying, would seem expected for me, for the reasons mentioned in the previous paragraph. That is also not related to physics or my person: as you pointed out in your post, Maple 2018.2 is already having trouble to run in that not-maintained ancient interface. Interfaces developed more than 20 years ago typically don't work 100% or at all in nowadays operative systems, a situation standard in software. You could still argue that "Classic" is included in the distribution of Maple (not for Macintosh since many years). Yes, but you know it is not maintained anymore and that is not the interface Maplesoft indicates to use with the Maple system, since years.
Then if for you, using the ancient "Classic" interface, is relevant for any reason, working with the last Maple that runs fine for your purposes in that interface would be the way to go, I suppose. Otherwise, I suggest you to start using the Standard interface, distributed with the Maple system, intended for its use, and well maintained by Maplesoft.
Maybe of help for you in that transition: open the preferences of the Standard interface, the one distributed with Maple and maintained by the company, and choose to use worksheet instead of document mode. If you prefer, also choose to use 1D math input (so-called Maple Notation). These two things already make the Standard interface distributed with Maple nowadays work primarily as that ancient "Classic" one, as said not recommended and not maintained anymore for many years. If the remaining differences are still important for you then, unfortunately, I have nothing else to suggest you.