Curious if you have inspected the battery and other FPC connectors on the motherboard for any type of damage such as bent, burnt, broken or missing pins, broken latch on the FPC connectors, etc. Also check flex cables for any damage. Have you tried reseating the battery's connection on the motherboard to see if it may have a loose connection. In a lot of cases the orange blinking light can signal an issue with the battery or it's connection and if it's properly communicating with the motherboard. It can be caused from a bad battery or if the battery is not properly communicating with the motherboard due to a damaged cable, connector, bad battery, or other possible issues on the motherboard or battery's small enclosed protective circuit board that the batteries flex cable is solder to. It is also possible you received a bad replacement battery which could be why you get the same results. There are many factors to consider but an orange blinking led in the HTC one m8 usually points towards a communication issue with the battery. Hope this helps.