The problem for the British at Arnheim with regards to their drop zones was purely one of a very specialized radio system codenamed Rebecca / Eureka. This system was designed to be placed on the drop zone and then left to run on its own. Transport aircraft would then know the particular designated frequency the transmitter was on and be able to home on it with a great degree of accuracy allowing them to drop precisely on the target.
Unfortunately, at Arnheim the system failed for a number of reasons forcing the transport planes to drop their supplies by visual indication; a much poorer and inaccurate method.
Of the drop zones, the following results were noted:

L Lost by D+2 and had problems with partially being screened by trees.
S Lost on D Day due to a glider crashing into the beacon.
X1 Lost on D+1 due to enemy fire and the drop zone being overrun.
X2 Lost on D+1 due to enemy fire and the drop zone being overrun.
V Lost on D+3 but restored the next day. Operated intermittently to save batteries and often was off when transports arrived due to scheduling errors.
Z Failed on D Day due to the operator being missing in action.


This sounds much more plausable than interference from iron deposits and due to the results coming from a report concurrent with the actual operation.

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