Hello CJ

If you google limiting the search domain into Gutenberg (sites for e-books), you will find 12 sites for "had trouble in finding …" against 27 sites for "had trouble finding …". And OED gives a quote for both "have trouble in X-ing"(1898) and "have trouble in X-ing" (1967).  These things suggest "have trouble X-ing" is an ellipsis of "had trouble in X-ing ". "Spend time X-ing" seems also to be an ellipsis of "spend time in X-ing" rather than "spend time on X-ing". In the Gutenberg, "spend time X-ing" and "spend time in X-ing" appear with almost equal frequencies.

You can get about 30 pages of "a position of teaching English" on Google. But somehow all of them appear in the pages with titles written in Chinese. There is no page using "a position of teaching Spanish", although there are 100 sites where "a position teaching Spanish" is used. As for other possibilities, I didn’t study them. If you English speakers omitted everything arbitrarily to coin a new collocation, as you are suggesting in the previous post, I wouldn't learn English grammar anymore.

Anyway thank you for your kind comments.

paco

Hi, KoMountain

Thank you for the nice comment and the kind advice.

be busy (in) -ing / have difficulty (in) -ing / have struggle (in) -ing / have a good time (in) -ing
have fun (in) -ing / spend time (in) -ing / have trouble (in) -ing
I think the deletion of 'in' from these phrases might be quite natural for English speakers (even non-native learners).
     [1] He was busy in writing messages on the Forums.
     [2] He was busy writing messages on English Forums.
     [3] He was busy while writing messages on English Forums.
The two "writing" in #1 and #3 are syntactically different. The "writing" in #1 is a gerund and the "writing" is a present participle. But the two sentences are almost the same, because "in X-ing" is semantically similar to "while X-ing". This would be the reason why the sentence #1 is transformed into #3.

Komountain wrote:

This relative unfamiliarity apparently causes us to wonder why the construction like 'a position teaching' is possible. I believe the only way for us non-natives to tackle this issue is to accept the peculiarity underlying those expressions. Languages often contain some elements beyond logical explanation. That's why learning a foreign language is interesting at one moment and frustrating at the next.

I completely agree. I often get frustrated when I come across a collocation I cannot understand logically. But I have to be patient as much as you.

paco