What exactly does this mean? DRAMs are DRAMs. The early DRAMs were Hitachi 4864, and the later large Apple branded chips were 4264 as well. Apple used DRAM from many sources. Larry Pina even indicates 4164 works in the 128K. The presence of an Apple silkscreen only indicates Apple got a deal on a batch of it, not any kind of special specs.
Gubbish - I have a 128K logic board with a similar problem with the stripes and garbage on the right side of the screen. In my case, it was a 128K upgraded to a 512K, and has since had it's mini-Mux removed, but the board was not repaired. I presume you've opened your 128K by now and inspected the logic board. If not, you should definitely do so, as the problem may be just that evident.
FYI, 256 DRAM chips are for 512K, but can also be used without a multiplexing array to achieve 128K, though I'm not sure I would mix-N-match them.