tl;dr edition: BB and SBB currently generate double-to-triple BC on most units in global bar a few exceptions noted in the post.

Testing with /u/HimekoTachibana has shown that drop checks on BB and SBB are currently tied to the amount of drop checks on the unit's normal attacks instead of the specific value tied to the BB and SBB. This testing has only been done on the Amazon version, but if anybody wants to try it on the others, Elza should be able to consistently fill her own SBB solo with Sol Creator and herself as leader. Just take her into a trial by herself, pop a Fujin and use SBB and she should fill up.

For example, this means that Elza, who normally has the following values:

• Normal: 3 DC/Hit, 30 total
  
• BB: 1 DC/Hit, 13 total
• SBB: 1 DC/Hit, 30 total

Currently has the following values:

• Normal: 3 DC/Hit, 30 total
• BB: 3 DC/Hit, 39 total
• SBB: 3 DC/Hit, 90 total

This has resulted in a general buff to the majority of units. The following units are nerfed by the change:

• Douglas - BB now has 1 DC/hit instead of 2 (Douglas is the only 6* unit with 1 DC/hit on normals...)
• Hogar - SBB now has 4 DC/hit instead of the intended 13 (still buffed from before the update). BB, however, has 4 DC/hit instead of 2/hit.
• Mifune - SBB now has 2 DC/hit instead of the intended 25 (still buffed from before the update)
• Dilma - SBB now has 5 DC/hit instead of the intended 12
• Loch - SBB now has 2 DC/hit instead of the intended 10
• Rowgen - SBB now has 20 DC/hit instead of the intended 30 (But BB is up to 20 from the intended 18)
• Will - SBB now has 2 DC/hit instead of the intended 3 (poor, poor Will)

The largest buffs are present on these units:

• Elza: Gained 26 drop checks on BB, gained 60 drop checks on SBB
• Eze: Gained 32 drop checks on BB, 40 drop checks on SBB
• Lario: Gained 13 drop checks on BB, gained 40 drop checks on SBB
• Kuda: Gained 36 drop checks on BB, gained 48 drop checks on SBB
• Farlon: Gained 27 drop checks on BB, 36 drop checks on SBB
• Maxwell: Gained 33 drop checks on SBB, none on BB (BB was already 2/hit). Maxwell's an odd one because Gumi already bugged out her DC and then fixed it again recently and some people may think she's just the same as before the change...
• Cardes: Gained 33 drop checks on SBB
• Melchio: Gained 30 drop checks on SBB
• Stya: Gained 30 drop checks on SBB
• Len: Gained 30 drop checks on BB, 40 drop checks on SBB
• Rin: Gained 22 drop checks on BB, 25 drop checks on SBB

and many more besides, too. Most units have at least gained drop checks equal to their BB/SBB hit counts, unless they already had more than 1 drop check per hit (e.g. Maxwell's BB, Arus/Nemia/Lilith's SBB).

This won't be fixed without an appstore update (game client issue, not data issue), and pretty much means the game is currently on easy mode. Case in point, you can currently do the Hadaron infinite with only one BC gen lead (plus the usual spheres) and it'll be relatively stable; you can run Shera x Xentar with dual Cardes and maintain her SBB for 100% mitigation with 100% uptime on Shera (vs dark only, but still, 100% uptime on 100% mit). Most BBspam strategies that maintain vs 2 now maintain vs 1. HimekoTachibana autobattled Maxwell until 10% HP using a relatively normal squad (Dual Rin leads, Elza, Elza, Lario, Darvanshel), had nearly 100% SBB fill rate and only failed because of being screwed by RNGesus several times along the way (would've been able to win by actually using items to revive the units that got focused after Rune).

This has no effect on normal attacks, so it's not going to break the game in arena at least, but it does mean trials are far easier currently than they were before.

As for how you can avoid it? You really can't, so I can't see any ban waves happening for this.