YES

Problem:
 a(a(a(b(x1)))) -> b(a(b(a(x1))))
 b(b(a(x1))) -> a(a(a(b(x1))))

Proof:
 String Reversal Processor:
  b(a(a(a(x1)))) -> a(b(a(b(x1))))
  a(b(b(x1))) -> b(a(a(a(x1))))
  Bounds Processor:
   bound: 6
   enrichment: match
   automaton:
    final states: {2,1}
    transitions:
     b3(162) -> 163*
     b3(134) -> 135*
     b3(84) -> 85*
     b3(136) -> 137*
     b3(86) -> 87*
     b3(143) -> 144*
     b4(314) -> 315*
     b4(239) -> 240*
     b4(241) -> 242*
     b4(191) -> 192*
     b4(186) -> 187*
     b4(308) -> 309*
     b4(243) -> 244*
     b4(193) -> 194*
     b4(188) -> 189*
     b4(300) -> 301*
     b4(260) -> 261*
     b4(230) -> 231*
     a4(257) -> 258*
     a4(227) -> 228*
     a4(187) -> 188*
     a4(259) -> 260*
     a4(229) -> 230*
     a4(189) -> 190*
     a4(258) -> 259*
     a4(228) -> 229*
     b0(2) -> 1*
     b0(1) -> 1*
     a5(281) -> 282*
     a5(248) -> 249*
     a5(285) -> 286*
     a5(280) -> 281*
     a5(250) -> 251*
     a5(302) -> 303*
     a5(282) -> 283*
     a0(2) -> 2*
     a0(1) -> 2*
     b5(272) -> 273*
     b5(247) -> 248*
     b5(249) -> 250*
     b5(283) -> 284*
     b1(50) -> 51*
     b1(45) -> 46*
     b1(62) -> 63*
     b1(276) -> 277*
     b1(64) -> 65*
     b1(24) -> 25*
     b1(19) -> 20*
     b1(4) -> 5*
     b1(151) -> 152*
     b1(6) -> 7*
     b1(145) -> 146*
     a6(294) -> 295*
     a6(296) -> 297*
     a1(65) -> 66*
     a1(5) -> 6*
     a1(47) -> 48*
     a1(22) -> 23*
     a1(7) -> 8*
     a1(49) -> 50*
     a1(31) -> 32*
     a1(21) -> 22*
     a1(63) -> 64*
     a1(48) -> 49*
     a1(23) -> 24*
     b6(306) -> 307*
     b6(298) -> 299*
     b6(293) -> 294*
     b6(295) -> 296*
     b2(60) -> 61*
     b2(35) -> 36*
     b2(107) -> 108*
     b2(77) -> 78*
     b2(72) -> 73*
     b2(74) -> 75*
     b2(278) -> 279*
     b2(153) -> 154*
     b2(310) -> 311*
     b2(245) -> 246*
     b2(43) -> 44*
     b2(33) -> 34*
     b2(155) -> 156*
     a2(75) -> 76*
     a2(97) -> 98*
     a2(57) -> 58*
     a2(104) -> 105*
     a2(59) -> 60*
     a2(34) -> 35*
     a2(106) -> 107*
     a2(36) -> 37*
     a2(73) -> 74*
     a2(58) -> 59*
     a2(105) -> 106*
     a2(95) -> 96*
     a3(217) -> 218*
     a3(304) -> 305*
     a3(87) -> 88*
     a3(219) -> 220*
     a3(164) -> 165*
     a3(159) -> 160*
     a3(291) -> 292*
     a3(161) -> 162*
     a3(208) -> 209*
     a3(168) -> 169*
     a3(160) -> 161*
     a3(312) -> 313*
     a3(85) -> 86*
     1 -> 31,19
     2 -> 21,4
     6 -> 95*
     7 -> 45*
     8 -> 44,5,1
     20 -> 5*
     21 -> 43*
     24 -> 57,47
     25 -> 35,6,32,2
     31 -> 33*
     32 -> 22*
     35 -> 168*
     36 -> 77,62
     37 -> 44,85,73,5,1,25,2,21
     44 -> 34*
     46 -> 5*
     47 -> 72*
     50 -> 97*
     51 -> 2,32
     57 -> 84*
     60 -> 164,104
     61 -> 188,86,37,25,35,8,5,32,2,21,4,43,22,1,19,33,6
     66 -> 44*
     74 -> 217*
     75 -> 155,151
     76 -> 135,85,51
     78 -> 34*
     86 -> 219*
     87 -> 153,145
     88 -> 192,187,144,108,61,6
     95 -> 136*
     96 -> 58*
     97 -> 134*
     98 -> 58*
     104 -> 143*
     107 -> 159*
     108 -> 2,21,4,43,32,6,8,5,1,19,33
     135 -> 85*
     137 -> 85*
     144 -> 85*
     146 -> 5*
     152 -> 5*
     154 -> 34*
     156 -> 34*
     159 -> 191*
     162 -> 227,208
     163 -> 190,188,88,86,8,66,37,25,1,2,21,4,43,64,32,5,31,6,35
     164 -> 186*
     165 -> 160*
     168 -> 193*
     169 -> 160*
     188 -> 291*
     189 -> 245*
     190 -> 248,244,163,37,73,1,31,19,33,5,25,85,64
     192 -> 187*
     194 -> 187*
     208 -> 243*
     209 -> 160*
     217 -> 239*
     218 -> 160*
     219 -> 241*
     220 -> 160*
     227 -> 247*
     230 -> 285,257
     231 -> 190,163,188,88,86
     240 -> 187*
     242 -> 187*
     244 -> 187*
     246 -> 34*
     249 -> 304*
     250 -> 278,276
     251 -> 299,294,273,261,231,86
     257 -> 272*
     260 -> 280*
     261 -> 88*
     273 -> 248*
     277 -> 5*
     279 -> 34*
     280 -> 298*
     283 -> 302*
     284 -> 190,163
     285 -> 293*
     286 -> 281*
     291 -> 300*
     292 -> 160*
     295 -> 312*
     296 -> 310*
     297 -> 307,294,284
     299 -> 294*
     301 -> 187*
     302 -> 306*
     303 -> 281*
     304 -> 308*
     305 -> 160*
     307 -> 294*
     309 -> 187*
     311 -> 34*
     312 -> 314*
     313 -> 160*
     315 -> 187*
   problem:
    
   Qed