Zcash -- Missing funds after sending a shielded transaction

[darkerego]

I have an issue that I have reached out to the unstoppable wallet support team about but have received no response for about a week now. Several months ago my client had transferred a large sum of zcash to his unstoppable wallet. Then he proceeded to send a transaction to a shielded address. The transaction succeeded, the recipient received the funds that were sent, but the remaining change amount, which was no small sum of money, seems to have vanished. The wallet is unable to find the remaining funds. These are the only logs related to zcash transactions that I have:

 - Send-ZEC:d515b619-4f1b-4f77-abd9-c78758b8282b:
     - 283: 2024-08-11 12:04:04.208 click
     - 284: 2024-08-11 12:04:04.230 call synchronizer.sendToAddress

   - Send-ZEC:a683c1f5-8d02-453e-8c5e-e2d5db4dddb0:
     - 286: 2024-08-11 12:05:38.916 click
     - 287: 2024-08-11 12:05:38.940 call synchronizer.sendToAddress
     - 288: 2024-08-11 12:06:02.227 failed: java.lang.RuntimeException: Error creating transaction proposal: Insufficient balance (have 2670000000, need 2670005000 including fee)
cash.z.ecc.android.sdk.internal.jni.RustBackend.proposeTransfer(Native Method)
cash.z.ecc.android.sdk.internal.jni.RustBackend.access$proposeTransfer(RustBackend.kt:22)
cash.z.ecc.android.sdk.internal.jni.RustBackend$Companion.proposeTransfer(Unknown Source:0)
cash.z.ecc.android.sdk.internal.jni.RustBackend$Companion.access$proposeTransfer(RustBackend.kt:394)
cash.z.ecc.android.sdk.internal.jni.RustBackend$proposeTransfer$2.invokeSuspend(RustBackend.kt:313)


   - Send-ZEC:e7451c76-afbf-4e40-aa88-c360d832b4a7:
     - 289: 2024-08-11 12:06:34.127 click
     - 290: 2024-08-11 12:06:34.162 call synchronizer.sendToAddress
     - 291: 2024-08-11 12:06:39.018 success

   - Send-ZEC:02812b29-db41-4954-9c74-97e684b19262:
     - 310: 2024-08-17 02:42:28.064 click
     - 311: 2024-08-17 02:42:28.114 call synchronizer.sendToAddress
     - 312: 2024-08-17 02:42:32.974 success

So far we have tried re-syncing the wallet and importing the mnemonic into another device, as well as with other zcash wallets, and still the funds are not present. Can anyone explain what happened and how to fix it?