There is irregularity in vowel harmony after some words of Arabic origin: saat -i, hal -i, harf-i, kalp-i, usul -ü, alkol -ü, and some others. The rule is connected to the last consonant of the word: If it is a non-emphatic consonant, front vowels are used, if it is an emphatic one then back vowels are used. (In the case of harf and kalp, front vowels are used because the Arabic "a" in these words is short and often prononced like an open /e/.) The rule seems to extend to some words of non-Arabic origin like hol -ü and kontrol -ü. The most useful part to remember about this rule is about the letter l: If it is thin, then a front vowel is used, even if the preceding vowel is a back vowel.
Well, not on 31 June 2020. And I was thinking about (not) putting that "my" in my translation, but I used it in the end, because there is "BENIM kontrolüm altında" in the Turkish sentence. That benim is, as far as I know, not necessary, so using it stresses, that everything is under MY control...
If you notice ‘benim. .....um’ is the possessive. The sentence is read as ‘Everything is under my control.’ Possibly the correct translation for ‘Everything is under control.’ is ‘her şeyi kontrol altındadır.’ However, if the first person, who is in authority, states ‘Everything is under control.’ then it means that he has sorted out the situation.
It looks like it could be another partial borrowing from French, where contrôler also can mean "to check, verify,"
Il faut contrôler ma voiture. --I have to check my car.
And of course at the Louvre or the "Bozar" in Brussels you'll see a sign directing you to contrôle des tickets, referring simply to the spot where they check and scan what you've downloaded onto your phone,