MaTeX stopped accepting certain font sizes

My system: Windows 10, Mathematica 11.2

Problem: I have been using the fine MaTeX paclet to get nice symbols on my plots. As I scale the images in a TeX-document after exporting them in EPS, I need to adjust the FontSize. So far things have worked out the way I wanted them to. But this week Mathematica has been acting up.

A command like

ec = ContourPlot[y^2 == x^3 - 5 x + 6, {x, -3.5, 3.5}, {y, -3.5, 3.5},
Frame -> False, Axes -> True,
AxesLabel -> {MaTeX["x"], MaTeX["y"]}]


works just fine, produces the expected image with nicely rendererd AxesLabels. But when I try

ec = ContourPlot[y^2 == x^3 - 5 x + 6, {x, -3.5, 3.5}, {y, -3.5, 3.5},
Frame -> False, Axes -> True,
AxesLabel -> {MaTeX["x", FontSize -> 18],
MaTeX["y", FontSize -> 18]}]


instead, I get a strange message with a tiny garbage image followed by a text like "MapThread[...". Having isolated the problem, the next thing to do was to try the input

MaTeX["x", FontSize -> 18]


This gave the following message that is all Greek to me, but hopefully somebody here can make sense out of it. I omitted most of the contents of the GraphicsBox for it's rather long. If judged essential, I will copy/paste all of it.

MapThread[ Show[#1, ImageSize -> {#2, #3}, BaselinePosition -> Scaled[(#4 + MaTeXPrivate$$psfactor)/#3]] &, {{\!$$\* GraphicsBox[ AspectRatio->Automatic, ImageSize->{12., 24.}, PlotRange->{{0., 11.97}, {0., 23.51}}]$$}, 0.996264 (2 + InterpreterDependentTypesPackagePrivatecoerced$$5234), \ {23.5118}, {6.45585}}]

Search: It is not impossible that my problem is related to that of this question. However, Szabolcs' diagnosis does not seem to fit here given that MaTeX in the exact same notebook worked a week ago. Therefore it is unlikely that for example Scandic letters in the path name would play a role. Furthermore, the path to this notebook is all ASCII-characters anyway.

Update:

More testing:

It seems to me that the choice of FontSize plays a role.

In a virgin session, the first call to MaTeX, asking for FontSize->16 greeted me with the following:

Fold::normal: Nonatomic expression expected at position 3 in Fold[Insert[#1,{},#2]&,MapThread[Replace[#1,Failure[InterpreterInternalPackagePrivateargs___,InterpreterInternalPackagePrivatea:Blank[<<1>>]]:>Failure[InterpreterInternalPackagePrivateargs,Join[InterpreterInternalPackagePrivatea,Association[<<2>>]]]]&,{<<1>>,{8.90271}}],InterpreterDependentTypesPackagePrivatepos\$3165].

Together with a lot of messages:

Symbol::argx: Symbol called with 0 arguments; 1 argument is expected.

Next, when I asked for an 18-point font, I got the plot together with typeset strings all right. But at the bottom of that cell there was something extra starting with Show[#1, ImageSize->{#2,#3},...

Next, when I asked for a 20-point font. THERE WERE NO PROBLEMS.

So has something destroyed my collection of fonts this last week?

A clue to the above test was that copy/pasting the snippet from Szabolcs' page worked as prescribed. So Magnification -> 2 works fine.

• FWIW I have been using MaTeX within the same installation of Mathematica since August. Mostly in the same selected folders. – Jyrki Lahtonen Nov 3 '19 at 11:49
• Superficially, it looks like an issue with Mathematica itself (all that internal Interpreter stuff), not MaTeX, and not actually related to the font size. Do try a ClearMaTeXCache[]. I am going offline in a couple of hours and won't be around for about a week, so unfortunately I can't dig into this now. – Szabolcs Nov 3 '19 at 15:25
• P.S. 1. I can't reproduce the problem. 2. The Mathematica version may be relevant. 3. The "Symbol called with 0 arguments" reinforces my suspicion that this is a bug in Mathematica. It will likely temporarily go away with a kernel restart ... – Szabolcs Nov 3 '19 at 15:27
• Thanks @Szabolcs. Yes my experiences from last Friday (when I temporarily had the same problem), and further testing now both indicate that this is an on/off thing. Just a few minutes ago I got a few of the offending font sizes to work. I will report, if I find something reproducible. – Jyrki Lahtonen Nov 3 '19 at 15:48

Quiet[MaTeX["x"]];

• ClearMaTeXCache[] definitely helps. For a reason I cannot understand I need to give that command twice. Or, doing it at the beginning only will still produce that error message. But, giving it again, and then reinputting the Plot-command makes the problem disappear. I am accepting this for now as a fix, but I don't think the problem is completely understood yet. Of course, I don't know the inner workings of MaTeX. – Jyrki Lahtonen Nov 25 '19 at 9:48