Indeed!
Long time ago, I have found similar problem due a test: I did MOVX to external RAM and read back value from same address at next command. The idea was that SRAM had not selected for that address range. Something like:

MOV DPTR,#NO_SRAM_ADDR
MOV A,#0x55
MOVX @DPTR,A
MOVX A,@DPTR

Here NO_SRAM_ADDR is the address where no external device presented. I was surprised: I read back not 0xFF but the low part of NO_SRAM_ADDR, wow! (= But when I have inserted one or more NOPs between those two MOVXs then I read stable 0xFF.
Sometimes, users do not pay attention that X2 mode gives us high frequences and requires some additional attention. For example, rise and falling edges are very short at high freqs and it may generate wave dimming with capacity of board wires/lines.
So from that test upto now I always use buffers (here: 74LS245) for data/address bus and other signals which go from MCU to external hardware.
Good days!