Odd
Normally any gear BUT first will slide in well enough when cold, with reverse often balky as well.
I usually use 4th from cold, as it's a straight back move without pushing to the side and it slides up & over into 1st easily. Higher the better for the purpose, so I suppose 5th would work - never tried it as it wasn't needed and it's an awkward shift by comparison. When stopped at a light and 1st doesn't go, usually use second since it already was to the left for first (straight move back).
Not going into first happens MOST in the cold, but it can happen randomly at any time. When cold it's usually from gears spinning too much, and extra sticktion from cold oil. When warm things can STOP spinning easily, and letting the clutch out again momentarily can help get in gear when at a stop. They don't always mesh perfectly when stopped. Row through all gears with engine off, and there's likely at least one that doesn't go in smoothly. Trying different ones even then moves things JUST enough to get into the prev. balky gear.
IDK why yours might be particularly balky, that usually happens ONLY when someone uses gear oil instead of the Synthetic MTF that's recommended. Even Mobil One in a 50W version works well in these, but regular gear oil is a no-no. I know you mentioned using the official Ford 'honey' that's not cheap, so that shouldn't be an issue.
Mine is only a PITA at times for 1st/rev when stinkin' cold, the rest of the time it shifts nicely - actually like the nice click click of shifting it. BUT I typically 'row' it into first at a stop without thinking about it as needed (use first & second until it goes in if needed) and it takes concentration for 'testing' after talking about it here to try direct to first until it gives me grief to make a note of.
Every time I say it seldom happens, then I'll see an odd balk into first at a stop. Only a PITA if I waited until the light already turned and want to hurry it, then might need to use 3rd or 4th before first as it balks at a quick 2-1 (grin). Never does it when not in a hurry, as the automatic move to 4th then back to first takes over when resistance is felt.