Setting up ZX-Spectrum "Leningrad 1"

Hello KingOfEvil I collected my copy of L-1 here. I started making improvements. Signal correction SCR. As in the book above, I added a chain for 1 leg IR9 to the RC gap. At a certain capacity value, the missing vertical line in the icon "(C)" of the splash screen appears, but at the same time at the very left edge of the screen (not border) a vertical stripe appears about a pixel wide, about whole screen (not raster). Moreover, this strip has some color, what - say I can’t, because the connector is soldered directly to the outputs of the multiplexer without disassembly flowers. Maybe there is something else that needs to be corrected, or is this the fate of the L-1?