Well sure they have issues. Ukraine's economy is quite poor so they can't spend much on their military. They are also presently at war with Russia and their weapons factories are often close to the Russian border and sometimes used to buy parts and materials from Russia proper (the relations date back from the USSR). So of course they're having a hard time fulfilling the order. But AFAIK the Ukrainians have always fulfilled their weapons deals in the past. There may be delays but they've always done their part as long as they get paid for it. One example is the deal with Pakistan with the T-80UD a couple of years back. When Russia denied them some critical parts the Ukrainians just made their own replacements locally. They have some good talent on engines and gas-turbines. Their tank, naval, and aircraft industries are presently mostly export oriented.
The T-90 has had its own issues as well. The Indians complained there was a wide variation between tanks. Some had turrets installed different from the original specification. Quite a lot of them were in fact remanufactured T-72 chassis. So it isn't just Ukraine that does this. There's quite a lot of ex-USSR equipment lying around so of course they'll reuse it as much as possible.