First you should note that your phone is heavy relative to a record and this will negatively impact the WF test on most beograms due to their lightweight construction, floating suspension and low torque. To use that app you need to readjust the suspension so it’s free and level when the phone is centered over the spindle and that the belt is centered on the pulley and platter. You should also also make sure the motor pulley and platter edge are clean. Finally, unless you got the belt from a legitimate B&O parts site, I would suspect it.

Yes, I've found that the TX2 is especially sensitive to weight, but anecdotally, not so much the 1700. In fact, the 1700 seemed to hum along quite nicely even when I put a substantial 370g record weight on it, just as a test, mind you. The TX2 screams bloody murder with such a weight.  Anyway, just now I cleaned the motor pully and platter edges on the 1700 and gave it another go with the app. Dang. Now the app measures w/f at .44.   Doh!  :) Guess I can try a different belt. If you've got a recommended vendor, please let me know. Oh... true story... I used the app to test a direct drive vintage sony (ps-lx2) I bought for $25 for non-playback purposes. Just needed something that would spin. Anyway, the sony tank won the w/f competition easily with a score of .12!!

So... three things I've done:

1. Ordered a replacement belt from Beoparts.
2. Downloaded WFGUI and experimented with it a bit. (Lots of 3150hz test tones out there, by the way.)
3. Ordered the Stereo Review Test Record (vintage 1979) from Discogs.

Let's see what we learn!  

If putting such a weight on it is not disrupting its suspension and belt running location, then its suspension height is not correctly adjusted.  Such a weight requires readjustment to compensate. Non-suspended turntables such as direct drives do not have this requirement.  The WFGUI with a test record and the DIN filter should better reflect the true performance. If you get a good belt and everything is adjusted properly and still seeing W/F>.2 then I would suspect the motor bearings may need a new oill suffusion or replacment.

Funny enough, I found your forum post as I was having serious wow and flutter issues with a Beogram 1700 that I just picked up. After recapping the board and adding a new belt, I was lost. My rpm app would get readings of up to 3% w&f. After nearly tearing my hair out, I found the solution. For me, it was the motor. Removed the pulley and put a good drop of machine oil on it, running it using the TURN button. After reassembling, the table now runs like a beauty. Good luck with your issue!

Interesting! Can you post your w/f measurement after lubrication? I just popped off the pully and applied some oil. Let's see what happens! (Will measure later.)

I added a drop of oil to the motor, but found w/f slightly increased (as measured with my heavy phone running the RPM app). Stay tuned.

Logged results from today's WFGUI test w/Stereo Review test record. Note: Have not yet received new belt from beoparts. Will post new results with new belt in future. Hz        RMS    W/F 3157.6 0.1527 0.2552 3146.0 0.1040 0.2552 3156.9 0.1176 0.2552 3147.6 0.1221 0.2552 3154.1 0.1278 0.2935 3150.5 0.1248 0.2935 3150.0 0.1445 0.3161 3154.0 0.1216 0.3161 3148.0 0.1251 0.3161 3154.2 0.1273 0.3161 3148.1 0.1078 0.3161 3153.4 0.1385 0.3161 3149.6 0.1110 0.3161 3151.9 0.1129 0.3161 3152.9 0.1315 0.3161 3148.6 0.1187 0.3161 3155.4 0.1211 0.2604 3146.5 0.1267 0.2726 3155.6 0.1162 0.2726 3147.1 0.1307 0.2964 3154.5 0.1362 0.3145 3149.4 0.1180 0.3145 3152.1 0.1069 0.3145 3152.3 0.1134 0.3145 3148.4 0.1208 0.3145 3155.2 0.1457 0.3145 3145.9 0.1110 0.3145 3155.8 0.1348 0.3145 3146.4 0.1095 0.3145 3155.1 0.1119 0.3145 3148.3 0.1111 0.2886 3153.0 0.1314 0.2886 3151.5 0.0945 0.2886 3149.3 0.1126 0.2886 3153.9 0.1216 0.2886 3147.4 0.0891 0.2820 3154.6 0.1334 0.2502 3148.2 0.1164 0.2502 3153.1 0.1099 0.2502 3150.1 0.1390 0.2963 3150.5 0.1268 0.2963 3153.0 0.1353 0.2963 3146.7 0.1170 0.2963 3155.9 0.1252 0.2963 3145.3 0.1047 0.2963 3156.9 0.1448 0.2963 3145.7 0.0982 0.2963 3155.6 0.1474 0.2963 3147.8 0.1049 0.2963 3153.2 0.1137 0.2912 3150.7 0.1241 0.2912 3149.9 0.1205 0.2675 3153.2 0.1136 0.2675 3148.4 0.1201 0.2675 3153.4 0.1088 0.2675 3148.7 0.1153 0.2675

You need to adjust your speed as well.