Complaining that cards that are not on the list are causing problems can only get one reply, why aren't you using cards on the list
Check the PDF list here:
http://tascam.com/content/downloads/products/867/dr-70d_tested_media_list_r1_20150224.pdf
Note: Cards added to the tested list will always be cards that you can buy new now.
The DR-680mkII added SDXC support as well, but 32GB SD cards will be the sweet spot for price and performance going forward I think though.
It's not the end user's responsibility to see what media functions with the recorder. If you want me to be a beta tester, send me a free deck to test. I paid for mine with the expectation it functions to the stated specs printed in the manual. Tascam advertises the deck works with SD cards (64 MB to 2 GB), SDHC cards (4 to 32 GB) and SDXC cards (48 to 128 GB). I expect my recorder to function with name-brand, non generic cards that meet the minimum specs that are needed to write four channels at 24/96, which is at minimum a true class four card and most assuredly a true class 10. According to Tascam directly and their approved media list, it obviously doesn't work with all of these cards so can I return it to Tascam under warranty and request a refund since it isn't functioning to spec?
Also, I have some comments about the cards Tascam is recommending. Instructing us to buy anything under 16gb to couple with a four channel, 24 bit, 96 khz recorder is laughable and let's just pretend 4, 8 and 16gb cards aren't on the list because quite simply, that's insulting in the year 2015 and not realistic for the majority of applications that this deck is being used for.
So, that leaves us with
two 32gb cards that are approved by Tascam and here's their current cost as of 9/22/15 at B&H Photo.
$74.95 - 32gb SanDisk Extreme Pro SDHC™ UHS-Ⅱ Part # SDSDXPB-032G-A46
http://www.bhphotovideo.com/c/product/1030992-REG/sandisk_sdsdxpb_032g_a46_32gb_extreme_pro_sdhc_uhs_ii.htmlDiscontinued - 32gb Panasonic SDHC UHS-I (CLASS 10) R:90MB/s Part # RP-SDUC32GAK
http://www.bhphotovideo.com/c/product/1044453-REG/panasonic_rp_sduc32gak_32gb_sdhc_uhs_i_u3_card.htmlTherefore, in reality your recommended list of cards for us real world users of this machine consists of solely one card, that costs $2.34 per gb. Does that sound reasonable to you when the street price of the 70d is $200 and the average name brand, class 10, 32gb card is selling for less than $0.50 per gb?
The solution is simple, instead of jerking us around have the engineers use some precious man hours and update the firmware so the recorder, ya know, records.