Spectrum is unstable

Hello Dut_Norshi If you just leave it turned on, then nothing happens. And if you start downloading toys or demos, in some of them something happens reset For example, in the game Field of Miracles (with RoboCop), as soon as the lady comes out - reset occurs. Target Renegade resets as soon as run. Best View (latest version) is reset (or draws cubes) immediately after loading screensaver. Well, there are similar examples in games and demos. I ran the tests. All RAM regeneration tests say "Everything is OK" But: HorrorFasTest 1.04R It says that I have a Z84 processor (I have KR1858VM1 installed), and there is TurboSound. It doesn’t give any errors, but the computer often resets (especially if after the test configuration run memory regeneration test). SYSTEM TEST 4.30R. Collection of Crazy Tests! (c) Compowellcome, Chirchik 1999 Displays a message like this "The data bus of this Spectrum in IM2 mode in TR-DOS is clogged!" RAMDOCTOR v2.0 by Sergey Tyatin After the port #7FFD blocking test, at the next check it starts saying that I have Spectrum 48k Some TACT 0.1 test draws two masks and reboots the computer. Has anyone encountered such symptoms? Is the memory somewhere broken/buggy or anything else? Maybe there are some opinions on this matter? Thanks in advance!